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Factsheet

Diphtheria, tetanus and whole-cell pertussis (whooping cough) (DTwP) primary immunisations

Protect your child Be wise - immunise

Diphtheria, tetanus and whole-cell pertussis (whooping cough) (DTwP) vaccine for primary immunisation

This factsheet provides referenced information on diphtheria, tetanus and whole-cell pertussis (DTwP) vaccine. DTwP is usually given as a single injection with Hib (Haemophilus influenzae type b) vaccine. Information is provided on: · diphtheria, tetanus and pertussis infection; · DTwP vaccines and their effectiveness; · safety issues about DTwP vaccine; and · further reading. The DTwP vaccine used in primary immunisation is different from the diphtheria, tetanus and acellular pertussis (DTaP) vaccine used as a pre-school booster. Written in a question and answer format, and with a glossary explaining technical medical terms, this factsheet is designed to provide concise yet comprehensive information on these serious diseases and the vaccine that protects against them.

The diseases

Diphtheria, tetanus and pertussis (more commonly known as whooping cough) are all caused by bacteria or by the toxins (poisonous compounds) that these bacteria produce. The characteristics of each disease are summarised below.1

Diphtheria

Diphtheria is a disease that results from infection with bacteria called Corynebacteria diphtheriae. These bacteria are usually spread in droplets of moisture coughed into the air. The bacteria then multiply in the mouth or throat of uninfected individuals. Symptoms begin 1 to 5 days after catching the disease (see Table 1). The first sign is usually a mild sore throat and pain on swallowing. It is usual to experience a low-grade fever, nausea, vomiting, headache and a fast heart rate. In most cases the bacteria produce a powerful toxin (toxigenic diphtheria) that can destroy nearby tissue and cause a membrane of dead cells to form. This membrane may be firmly attached to the throat, tonsils or voice box (larynx), or may form in the nose. This membrane may narrow the airway, or it can become detached and block the airway completely so that the person cannot breathe. This may lead to death. The toxin can also travel through the bloodstream to the heart and nerves. Resulting damage to the heart muscle can lead to heart failure and sudden death. Nerves may be affected at different times: nerves to the throat are often affected during the first week of illness, making swallowing difficult; nerves to the arms and legs may become inflamed between the third and sixth weeks, causing weakness. Neurological complications occur in approximately 1 in 5 cases.2 Overall, 5 to 10 per cent of people who catch respiratory diphtheria die. Although the number of cases has decreased, the fatality rate has not fallen despite modern management.3 The skin can also be a site of infection. This form of diphtheria is caught through direct contact and is common in tropical countries. A shallow, non-healing ulcer forms which can be a source of infection for respiratory diphtheria in other people. Very rarely, toxin can be absorbed from the ulcer and travel through the bloodstream to cause similar symptoms to those described above. How serious is diphtheria? Table 1 shows the most common symptoms of diphtheria together with some of the possible complications. How common is diphtheria? Following the introduction of immunisation against diphtheria on a national scale in 1940 there was a dramatic fall in the number of notified cases and deaths from the disease (Fig. 1). Of the few reported cases these days of toxigenic diphtheriae infection, most were acquired overseas from countries where the disease is still endemic. The last reported death from C. diphtheriae in the UK was in 1994 in a 14-year-old boy who had visited Pakistan. Around the same number of infections caused by C. diphtheriae are currently caused by Corynebacteria ulcerans, but these are generally acquired in the UK. C. ulcerans is a bacterium related to C. diphtheriae. Toxigenic strains of C. ulcerans produce diphtheria that is indistinguishable from that produced by C. diphtheriae.

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Table 1 The symptoms of diphtheria

Most common symptoms Low-grade fever (less than 38.5°C) Inflammation of the throat (most commonly the pharynx but may also affect the larynx (voice box), or nose) Formation of an exudate (thick liquid) which forms a thick greyish membrane Swollen lymph nodes and glands (so called bull-neck appearance) Rapid, faint pulse Pale, shocked appearance Possible complications Respiratory obstruction Pneumonia Otitis media Sinusitis (inflammation of the sinuses) Acute systemic toxicity (organ failure) Myocarditis (inflammation of the heart) Peripheral neuritis (neural condition) Nephritis (inflammation of the kidney)

80,000

80,000

Immunisation began

70,000 60,000 50,000 40,000 30,000 20,000 10,000 0 1914 70,000 60,000 50,000

Notifications

Deaths Notifications

40,000 30,000 20,000 10,000 0

1924

1934

1944

1954 Year

1964

1974

1984

1994

2004

*Notifications up to 1985, laboratory-confirmed cases 1986­97 Source: Office of National Statistics; Public Health Laboratory Service

Figure 1. Diphtheria ­ notifications and deaths, England and Wales (1914­2001/02)

Tetanus

Tetanus (commonly known as lockjaw) is caused by a bacteria called Clostridium tetani. Unlike diphtheria and pertussis, tetanus is not passed from person to person. Spores of the bacteria are present in soil and manure and can be picked up quite easily, through a scratch, puncture wound, burn or more serious injury. Infection can develop in either minor or deep wounds (but it is very rare in the UK because of the high levels of immunisation). The bacteria release toxins which act locally at the site of an injury and on the central nervous system (CNS) to cause the disease symptoms. The majority of cases occur within 3 days to 3 weeks of exposure.

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Deaths

How serious is tetanus? The three characteristic types of symptoms are shown in Table 2. Table 2 The three characteristic symptoms of tetanus.

Affected area Localised (unusual) Symptoms Muscle spasms in a site close to the original injury. The first symptom is spasm of the jaw. Involvement of other muscles in the neck, back, abdomen and limbs may follow. Generalised painful contractions, like seizures, can occur. Outcome May persist for several weeks or months before subsiding. Death occurs in less than 1% of cases.4 Spasm of part of the voice box can cause immediate death. Other injuries, such as fractures, can be caused by the violent contractions. The disease remains severe for 1 to 4 weeks, then gradually subsides. Death may occur, with the rate being affected by age and immunisation status.5 Rare symptom that may progress to generalised tetanus with similar risks.

Generalised (occur in 80 per cent of cases)

Cephalic (relating to the head) (rare)

Usually associated with injury to the head. This leads to different areas of paralysis. Jaw spasms may also be present.

How common is tetanus? Tetanus immunisation was introduced into routine childhood immunisation in the mid-1950s in some areas and nationally from 1961. The disease had almost disappeared in children under 15 years of age by the 1970s.6,7 Tetanus in the newborn remains a public health problem in many developing countries. It is usually caused by infection of the umbilical stump due to poor hygiene techniques. Tetanus in the newborn no longer occurs in the UK and there have been no cases for over 30 years. The total numbers of cases of tetanus by age and sex in England and Wales from 1984 to 2002 are shown in Fig. 2. In a recent study in the UK, the highest incidence of tetanus during this period was in adults over 64 years of age, with no cases of tetanus reported in infants under 5 years of age.7 Most of the cases in the UK occurred following injury outdoors (e.g. in the garden). In virtually every case the person is unimmunised or incompletely immunised. Over the last 10 years, the number of cases of tetanus has been consistently low, with an average of six cases each year. (pers. comm. PHLS)

200 180 160 140 Number of cases 120 100 80 60 40 20 0 0-4 years 5-14 years 15-24 years 25-44 years 45-64 years 65 years+ Not known All Age groups

Males Females All

Source: reports to national tetanus surveillance PHLS CDSC

Figure 2. Tetanus by age and sex in England and Wales from 1984 to 2002

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Pertussis (whooping cough)

Pertussis is caused by infection with bacteria (called Bordetella pertussis) which are transmitted in droplets of moisture breathed out by infected individuals. The incubation period is between 6 and 20 days. Pertussis infection ranges from a mild disease to one that is serious and can result in death. The illness progresses from a catarrhal stage with symptoms that may be similar to a common cold, to coughing and choking spells that can lead to difficulty in eating, drinking or breathing.8 Most people do not have a raised temperature when they have pertussis. The coughing episodes (with characteristic `whoop') are exhausting and vomiting is common. The illness commonly lasts 6 to 8 weeks even when treated with antibiotics. A cough without the whoop may persist for many weeks. Minor complications include subconjunctival haemorrhages, epistaxis secondary to coughing, face oedema, ulceration of the tongue or surrounding area, and suppurative otitis media. Three forms of major complication can arise separately or together (see Table 3). How serious is pertussis (whooping cough)? The major complications of pertussis are shown in Table 3. Table 3 Major complications of whooping cough

Affected area Respiratory Symptoms The majority of cases of pertussis involve some degree of collapsed lung and/or pneumonia. Babies may stop breathing. Outcome Pneumonia may be severe enough to lead to death. Approximately half the deaths from pertussis are due to pneumonia. Those who survive usually do not experience permanent lung damage.9 Death, permanent brain damage or full recovery are each equally likely to result from this encephalopathy. Around two-thirds of children under 1 year of age who have whooping cough may be admitted to hospital. Up to 1 in 50 babies can suffer convulsions. Around 1 in 1000 may develop encephalopathy (affecting the brain).1 Severe weight loss may occur.

Central nervous system

The most common forms are altered consciousness or convulsions. This is thought likely to result from a lack of oxygen or small amounts of bleeding into the brain.

Nutritional

Repeated vomiting.

The severity of symptoms is related to age, with infection being most severe in infants. More than half of those infants under 1 year of age reported with pertussis are hospitalised.11 Approximately 1 in every 500 children under 1 year old with pertussis dies as a result of this illness: the risk is highest in younger babies.12 Although serious illness is less common in older children and adults, approximately 1 in 15,000 to 21,000 older children with pertussis may die, and adolescents and adults can get a prolonged unpleasant cough.13,14 Cases, and even deaths, may not be recognised and so these rates are probably underestimates of the real burden. The most recent estimate is of nine deaths per year in England from pertussis.15 Older children and adults with mild disease can transmit infection to vulnerable babies. How common is pertussis? Since the introduction of pertussis immunisation in the 1950s, the overall number of pertussis notifications has declined substantially (Fig. 3). However, pertussis re-emerged in the late 1970s following a scare (which

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proved unfounded) about the safety of pertussis vaccine. Fig. 3 shows how coverage of pertussis vaccine has varied since it began to be routinely measured in the late 1960s, and how quickly disease incidence increased when vaccination coverage fell.

200 180 160 Notifications (thousands) 140 120 100 80 60 40 20 0 1940

100 90 80 Vaccine coverage (%) 70

Notifications Vaccine coverage

60 50 40 30 20 10 0

1950

1960

1970 Year

1980

1990

2000

Source: Office of National Statistics; Department of Health Statistics Division

Figure 3. Pertussis ­ notifications and vaccine coverage for children by their second birthday, England and Wales (1940­2001/02) Despite the fall in pertussis to its current low level, it remains a significant cause of illness in the very young (Fig. 4), and mortality. Over the last decade there has been no fall in the number of pertussis notifications in young infants; the majority of hospital admissions due to pertussis have occurred in those under 6 months of age, some of whom were seriously ill and required admission to paediatric intensive care units.16,17

800 Notification rate (per 100,000 population) 700 600 500 400 300 200 20 100 0 1982 10 0 1985 1988 1991 Year 1994 1997 2000 100 90 80 Vaccine coverage (%)

All ages 0-2 months Vaccine coverage at 2 years

70 60 50 40 30

* For 2001, only the first quarter is shown. Source: Office of National Statistics; Department of Health Statistics Division

Figure 4. Pertussis ­ notifications in all ages and infants aged 0 to 2 years, and vaccine coverage at 2 years of age, England and Wales (1982­2001) Table 4 shows the annual number of hospital admissions from 1995 to 1999 due to pertussis infection in infants under 6 months of age and in those aged between 6 and 11 months. The numbers indicate that the burden of disease in those under 6 months of age remains high and shows how important it is that herd immunity is maintained to protect infants too young to be immunised.

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Table 4 Annual number of hospital admissions due to pertussis infection from 1995 to 1999.

Year 1995 1996 1997 1998 1999 Under 6 months 391 633 1171 616 564 6­11 months 53 79 94 61 67

Source: Department of Health, Hospital Episode Statistics for England.

Between 1995 and 1997, there was a significant increase in the proportion of pertussis infection in infants under 6 months of age rising from 6.3 per cent in 1991 to 19.1 per cent in 1997.18 The majority of deaths due to pertussis infection during this period occurred in babies who were too young to be immunised.13 Pertussis in older age groups, including young adults, is often not recognised and is much more frequent than suggested by notifications.15 Parents, and older unvaccinated siblings are passing pertussis on to younger children too young to be immunised.

The DTwP vaccine

What is DTwP vaccine? DTwP vaccine has been used in the UK since 1940. This vaccine is prepared from the toxins that are produced by diphtheria and tetanus bacteria. These toxins have been inactivated and rendered harmless (and are called toxoids) but are still able to induce immunity. These toxoids are combined with one or more strains (types) of whole pertussis bacteria that have been killed. As the whole pertussis bacteria are used, this type of vaccine is often referred to as `diphtheria, tetanus and whole-cell pertussis'. These ingredients are combined with aluminium hydroxide in order to increase the immune response and reduce the number of adverse reactions. All vaccines are independently tested at the National Institute for Biological Standards and Control for purity, potency and toxicity before they can be used. DTwP and Hib are tested separately and when combined together. What does this vaccine protect against? DTwP protects against diphtheria, tetanus and pertussis diseases. It is often combined with Hib vaccine and will protect against Hib disease at the same time. When are children routinely given the DTwP vaccine? The routine childhood immunisation schedule is shown in Table 5 with DTwP highlighted. Are additional doses of vaccine needed? Additional doses of diphtheria vaccine may be recommended more than 10 years after the last booster to people who are considered to be at increased risk because of contact with infected people, or who travel to countries where diphtheria is more common. Additional doses of tetanus vaccine may also be needed if individuals are travelling to countries where they may not be able to get the right treatment if injured. Currently, no additional doses of pertussis are required after the fourth dose.

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Table 5 Timetable of routine childhood immunisations.

When to immunise Two, three and four months old What is given Polio Diphtheria, tetanus and whole-cell pertussis and Hib (DTwP-Hib) MenC Measles, mumps and rubella (MMR) Polio Diphtheria, tetanus and acellular pertussis (DTaP) Measles, mumps and rubella (MMR) BCG (against tuberculosis) Tetanus and Diphtheria (Td) Polio How it is given By mouth One injection One injection One injection By mouth One injection One injection Skin test, then, if needed, one injection One injection By mouth

Around 15 months old Three to five years old (pre-school) 10 to 14 years old (and sometimes shortly after birth) 14 to 18 years old

How effective has the DTwP vaccine been? DTwP has been extremely effective in virtually eliminating diphtheria, preventing tetanus and bringing pertussis to the lowest ever recorded level (see Fig. 4). Although mild attacks of pertussis may occur in vaccinated children, protection against severe disease resulting in hospital admission is around 95 per cent.19 How long does the protection from DTwP vaccine last? DTwP protects children until they have their pre-school booster at 3 to 5 years. Five doses of tetanus vaccine are thought to protect for life. However, if a child or adult is injured and has a dirty wound, for example because the injury occurred outdoors, he or she may sometimes require additional protection with tetanus immunoglobulin or tetanus vaccine. How safe is the DTwP vaccine? The risks of any serious side effects are extremely low. Since 1991, over 22 million doses of DTwP vaccine have been distributed in the UK. As with all medicines, however, vaccines can have side effects but these have to be balanced against the consequences of catching the diseases. The next section describes the possible reactions in more detail. What adverse effects may be seen after DTwP? The types of reactions seen after DTwP are summarised in Table 6. Where adverse reactions do occur due to DTwP, they are most likely to arise 12 to 24 hours after the vaccine has been given. Symptoms that begin after 48 hours are unlikely to be linked to the vaccine and probably have another cause. Swelling and redness at the injection site are quite common and these occur more often with each successive vaccine dose.20,21 These reactions are substantially lower in children vaccinated on the accelerated schedule used in this country, compared with children vaccinated at older ages.22 About 1 in 100 children may become excessively sleepy after vaccination, or may cry for a prolonged period. This usually occurs within 12 hours after immunisation. More rarely a child may go pale, limp and unresponsive following DTwP immunisation: this occurs approximately in 1 in every 1000 to 6000 DTwP immunisations.23 Children who have been monitored following such reactions have been shown to have no lasting problems as a result. A study has shown that they went on to complete their DTP vaccinations without any problems.24

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Table 6 Side effects of DTwP vaccine.1,22,35

Common reactions Localised swelling, pain and redness (occurs in about 1 in 25 children) Mild fever ­ 1 in 2 children (less than 1 in 100 experience a fever over 40.5°C 24 to 48 hours after immunisation) Excessive sleepiness ­ 1 in 100 children (usually occurs in the first 12 to 24 hours) High pitched persistent/inconsolable crying (usually occurs within the first 12 hours) Pallor Cyanosis

Uncommon/rare reactions Febrile convulsions (occurs in around 1 in 10,000 to 16,000 children) Hypotonic-hyporesponsive episode (occurs in less than 1 in 1000 children), usually within 12 hours and may last for a few hours. Always resolves. Anaphylaxis (2 per 100,000 injections) Acute encephalopathy (2 per 1,000,000 injections)

Children may have a slight temperature after receiving DTwP vaccine. In cases where fever increases rapidly, a febrile convulsion may occur. A febrile convulsion is when a child has a type of fit brought on because of a high temperature. Febrile convulsion is a recognised reaction following DTwP vaccine, particularly after a third dose of the vaccine. In a recent study approximately 1 in 12,500 DTwP immunisations resulted in a hospital admission following a febrile convulsion.22 If a febrile convulsion occurs these symptoms are distressing but they have been shown not to lead to long-term problems.25 Are there any children who should not receive DTwP? There are very few children who can not have DTwP.26 If a child is ill, with a fever, immunisation should be postponed until the child has recovered. If a child has an evolving neurological condition they should be appropriately assessed. If necessary, pertussis immunisation may be delayed until the condition has become stable. This is to avoid wrongly associating the condition or its progression with the vaccine. There is good evidence that children who have had a reaction to a previous dose of DTwP can go on to complete their immunisations safely.27 If necessary, this can be carried out in a special clinic or in hospital. Where adverse reactions do occur, it can be difficult to assess the component of the vaccine responsible for the reaction and extra advice may be needed. Adverse reactions are most likely due to the pertussis component of DTwP. DTaP may be indicated following a severe local reaction, and if considered appropriate by a paediatrician or immunisation co-ordinator, DTaP can still be used after a severe general reaction to DTwP. Stable neurological conditions, like spina bifida or cerebral palsy, are not reasons to withhold DTwP. In fact, it is extremely important that children with such conditions are protected from diphtheria, tetanus and pertussis as the diseases may be worse for them than other children. Similarly, if someone in their family has some form of allergy or suffers from seizures (fits, convulsions) or another neurological condition, a child should still be given the DTwP vaccine.

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Parents should be encouraged to discuss these issues with the doctor, health visitor or nurse if they are unsure whether their child should be immunised. What should a parent do if their child is unwell after receiving DTwP vaccine? If a parent has any concerns about the health of their child after they have been immunised, particularly if they become seriously unwell, they should consult a doctor. It may be that the child is suffering from an illness that is totally unrelated to the vaccine. A few children may develop a mild fever after immunisation. Children should be treated for a mild fever by making sure they have plenty of cool drinks and by giving them paracetamol or ibuprofen liquid. Parents should be reminded to read the instructions on the bottle carefully and give the correct dose for their child's age. This is especially important for ibuprofen where different dosages are only appropriate for children of certain ages and weights.

Never give aspirin to children under 16 years of age.

If a child has a severe or unexpected reaction to the DTwP vaccine, this should be reported to the doctor, practice nurse or health visitor. If parents are concerned about their child after immunisation they should consult a doctor. It may be that the child is suffering from an illness that is unrelated to the vaccine. If a doctor, nurse, health visitor or pharmacist suspects that an adverse reaction to a vaccine has occurred in a child, they should report this to the Committee on Safety of Medicines, using the Yellow Card spontaneous reporting scheme. Why should children be immunised if these diseases are so rare? While diphtheria and tetanus are very rare and pertussis is uncommon in the UK and in most developed countries, cases can still present a threat. Children who are not immunised will remain at risk of getting these diseases throughout their life. In a number of countries, including the UK, cases of pertussis have increased substantially when immunisation uptake has fallen. Even when immunisation coverage levels are very high, the pertussis organism can still circulate; non-immunised or incompletely immunised infants are those most affected by this circulating disease.15,28 The chance of catching diphtheria in the UK is remote because immunisation coverage is high. However, travel to areas where the disease is endemic increases the risk. The few cases of infection with C.diphtheriae which have occurred in the last few years have all been imported from countries where the disease is still endemic. If vaccination coverage falls, diphtheria can come back very quickly as seen in Russia and the newly independent states in the 1990s. What is the risk of children getting tetanus if they are not immunised? The risk of catching tetanus following any injury is very small. The risk is highest if the injury is a deep puncture wound or contaminated with soil or manure. Due to the high levels of immunisation of children against tetanus over the last 50 years, most cases in the UK occur in unimmunised people who are injured outdoors, often older people. However, tetanus cannot be eradicated as it is always present in the environment. An unimmunised person is always at risk.

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What is the risk of children catching pertussis if they are not immunised? Pertussis still circulates in the UK population so unvaccinated infants and children and those who are too young to be immunised are always at risk of catching the infection. The chance of catching pertussis depends on a number of factors, including the number of susceptible people in the population, contacts between them and their age. The risk is not constant ­ it will increase and decrease. People who are not immunised will always be at increased risk. Pertussis in older age groups, including young adults, is often not recognised in the UK and is much more frequent than suggested by notifications. Parents, and older unvaccinated siblings may, therefore, pose a risk to their own babies.16,17 Can a child's body cope with so many vaccines at one time? As soon as a child is born it comes into contact with thousands of bacteria and viruses. A baby's immune system responds to all these challenges and prevents harm from the moment it is born. The vaccines that babies receive in the first year of life are just a drop in the ocean compared to the tens of thousands of immuniological challenges that babies have to cope with every day. It has been estimated that the immune system of each infant would have the theoretical capacity to respond to around 10,000 vaccines at any one time.29 In reality, of course, children receive nowhere near this number of vaccines. It has been predicted that if 11 vaccines were given to an infant at one time, then about 0.1 per cent of the immune system would be busy responding to the vaccines and only for a short period of time. Does DTwP vaccine contain mercury (thiomersal)? Yes, DTwP vaccine contains very small quantities of thiomersal, a mercury-containing compound used as a preservative. Because high levels of mercury compounds can be toxic, there has been public concern that thiomersal in DTwP vaccine can cause harm to the brain of young children. International scientific organisations have carefully looked at the evidence for the safety of thiomersal and concluded that there is no evidence of neurological harm caused by the very small amounts of thiomersal in vaccines. A recent review of the evidence by the UK Committee on Safety of Medicines concluded that there was no evidence that thiomersal-containing vaccines caused neurological problems.30 The only evidence of harm due to thiomersal in vaccines was a small risk of hypersensitivity reactions (that typically include skin rashes or local swelling at site of injection). Studies looking at the metabolism of ethylmercury (the mercury product in thiomersal) have shown that it is rapidly excreted from the body and does not easily cross the blood brain barrier.31,32 A recent study has looked specifically at whether the low levels of thiomersal present in routine childhood vaccines cause significant changes in the level of mercury in infants' blood.31 This study concluded that the levels of thiomersal did not raise blood concentrations of mercury above the safe values in infants. Furthermore, it showed that infants rapidly eliminated ethylmercury from their body following immunisation with thiomersalcontaining vaccines.

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Can children have the vaccine if they were premature? Yes, children who are born prematurely can be given DTwP vaccine at the same age after birth as other children. It is not necessary to wait until their corrected age. Children have been shown to mount a good response to the vaccine regardless of their gestational age at birth.33 Isn't there another pertussis vaccine available now? Yes, an acellular pertussis vaccine is available in the form of DTaP vaccine. This vaccine is routinely given as a pre-school booster. Why don't we use the acellular pertussis vaccine for routine primary immunisation? Efficacy trials have shown that the DTwP vaccine licensed and used in the UK primary immunisations gives a higher level of protection than the DTaP that is currently available. Children receiving DTaP were found to be about twice as likely to catch pertussis than those children vaccinated with DTwP.34 Evidence from efficacy trials in which acellular and whole-cell vaccines have been compared directly show that most are less efficacious than whole-cell vaccine such as the one used in the UK.34 Why do they use acellular pertussis vaccine for routine immunisation in the USA? Studies have shown that the DTwP vaccine licenced for use in the USA was less effective in their primary immunisation schedule (2, 4 and 6 months) than available DTaP vaccine.34 In addition, the DTaP caused less adverse reaction when given according to their schedule. Is there a link between DTwP and Sudden Infant Death Syndrome (SIDS)? This issue has been studied in great detail and the evidence does not support a link between DTwP and SIDS. The Institute of Medicine in the United States has reviewed the possibility of SIDS occurring as a result of immunisation with DTwP vaccine.35,36 They concluded that the evidence does not favour a causal link between DTwP and SIDS. Some studies have found that there was either no association with SIDS or even a lower risk in children who had been fully immunised.37-38 Is there a link between pertussis vaccine and long-term neurological illness? In the past, a broad range of neurological conditions had been linked to pertussis vaccine. The causes of many of these conditions are often unknown and they existed before the introduction of pertussis vaccines. The symptoms of many neurological diseases (e.g. seizure disorders) develop in the first year of life.39 It is easy to see why these conditions may be linked to vaccination. Reviews of published studies have found that the evidence does not support the suggestion of long-term neurological problems resulting from immunisation with pertussis vaccine.40-42 Whilst there is an increased risk of febrile convulsion after DTwP, there is no evidence that this produces brain injury or leads to epilepsy.41 There is evidence that children who experience a hypotonic-hyporesponsive episode or convulsions within 48 hours of DTwP immunisation do not suffer any serious long-term neurological damage.43,44 The nature and pattern of neurological symptoms with long-term consequences that have been observed shortly after immunisation with DTwP vaccine are no different from those that occur in children of the same age who have not been vaccinated.40

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Can pertussis vaccine cause epilepsy? It has been shown that DTwP vaccine can cause fever in children who have been immunised and that this may lead to convulsions.40 (See Table 6). The important issues are whether these convulsions can cause damage to the brain and whether they can lead to epilepsy. Febrile convulsions that occur after immunisation with DTwP vaccine are just like those caused by any fever. If a fever occurs after a DTwP vaccination in a child with a personal or family history of convulsions then it is more likely to experience a febrile convulsion than a child with no such history.21 However, there is no evidence that a febrile convulsion leads to epilepsy or harms the child.25,40 It is recommended, therefore, that such children are immunised with DTwP and that parents be advised on how to prevent and treat fever.26 Can DTwP vaccine `trigger' conditions in children? A baby may appear to be healthy and developing normally and yet actually have brain damage or metabolic, genetic or other problems that have not become apparent. There is no evidence that pertussis vaccine can cause or worsen any of these conditions. DTwP vaccine may appear to accelerate the appearance of some neurological symptoms but it does not increase the number of children who develop such symptoms overall.45,46 Is there a link between pertussis vaccine and asthma or allergy? There have been suggestions that pertussis vaccination increases the risk of asthma or other allergies.47,48 A study of 10,000 children examined the possibility of a link between immunisation against pertussis and subsequent development of asthma.49 Approximately 2 years after immunisation, no significant differences in the proportion of children reporting wheezing, itchy rash or sneezing were found in those given vaccine with or without a pertussis component. A 5-year follow-up study was conducted on a group of children who were born in 1970.44 Over 12,000 children were included in the study, of which approximately 86 per cent were fully immunised against pertussis. It was found that by age 5, those who were not immunised against pertussis had a statistically significant increased risk of developing wheezing (as an indicator of asthma) compared to those who were immunised against pertussis. The observed increased risk may have come about because pertussis vaccine had been withheld in those children already exhibiting an allergic disorder. There was definitely no suggestion that the risk of allergy was increased in children who had had pertussis vaccine. A recent paper examining over 160,000 children up to a maximum of 6 years of age found that children who received DTwP (and other routine childhood vaccines) were no more likely to develop asthma in infancy or childhood than those who did not receive DTwP.50 There is no evidence from well-controlled studies that vaccines cause asthma. The impact on the immune system from vaccines is tiny compared to the natural stimulus of all the infections, toxins and other proteins that occur every day. Is there a link between pertussis vaccine and deafness? There is no link between immunisation with DTwP vaccine and hearing loss.51

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Glossary of terms

Acellular vaccine

Without whole cells. An acellular vaccine contains only parts of cells which can produce immunity in the person receiving the vaccine (see DTaP).

Epiglottitis

Inflammation or swelling of the epiglottis that can cause a blockage of the airway which can be fatal.

Epistaxis

A nose bleed.

Adverse reaction

A side effect of a vaccine.

Febrile convulsion

Convulsion brought on by a high temperature or fever.

Antibodies

Proteins produced by the body to neutralise or destroy toxins and disease-carrying organisms.

Genetic

Inherited from parent.

Bacterium/bacteria

Single cell micro-organisms. There are many different types or strains of bacteria some of which cause disease. Others are essential for our bodies to work properly.

Haemophilus influenzae

The bacterium that causes Hib disease. It occurs in two forms ­ those with capsules (encapsulated) and those without (non-encapsulated). Serious disease is usually caused by the encapsulated organisms of which there are six types (a to f). Type b caused the majority of Hib disease before the vaccine was introduced. Non-encapsulated strains are mainly associated with ear and chest infections.

Cyanosis

Bluish coloration of the skin and mucous membranes, for example, the lining of the mouth, caused by too little oxygen in the blood.

DT

The combined diphtheria and tetanus vaccine.

Herd immunity

The protection conferred on individuals who have not been immunised because sufficient numbers of the rest of the population have been immunised.

DTaP-Hib

Combined vaccine that protects against four different diseases ­ Diphtheria, Tetanus, Pertussis (or whooping cough) and Haemophilus influenzae type b (Hib). Contains acellular Pertussis vaccine.

Hib

Hib is an infection that can cause a number of major illnesses like meningitis, blood poisoning and pneumonia. All of these illnesses can kill if they are not treated quickly.

DTwP-Hib

Combined vaccine that protects against four different diseases ­ Diphtheria, Tetanus, Pertussis (or whooping cough) and Haemophilus influenzae type b (Hib). Contains whole-cell Pertussis vaccine.

Hypotonic-hyporesponsive

Abnormal muscle slackness leading to excessive limpness and a lack of responsiveness to stimuli.

Immune response

The body's response to an immunisation or infection.

Diphtheria

Diphtheria is a disease that usually begins with a sore throat and can quickly cause problems with breathing. It can damage the heart and nervous system and, in severe cases, it can kill.

Immunisation

The priming of the body's immune system with a vaccine.

Meningitis

Meningitis is an inflammation of the lining of the brain. Hib can be a cause of meningitis and may also cause septicaemia (blood poisoning). Hib septicaemia differs from that caused by meningococcal bacteria in that there is only very rarely an accompanying rash. Babies and children under 4 years of age are at most risk from Hib meningitis or septicaemia.

Efficacy

The measure of a vaccine's effectiveness. It is measured by the proportion of those immunised who don't get a disease when exposed to it, or by the number of antibodies produced by the immune system.

Epiglottis

Flap of cartilage behind the tongue that covers the entrance to the windpipe when swallowing.

Metabolic

The body's metabolism is the sum of all the chemical processes taking place within it.

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Mortality

The death rate of a population or a group within it. Often expressed as so many deaths per 100,000 of the population.

Vaccines

Vaccines are manufactured in different ways using part of the germ or virus which causes the disease. Except very rarely (oral polio vaccine only) they cannot cause the disease for which they give protection.

Neurological condition

A disorder of the nervous system.

Whole-cell vaccine

A vaccine that is maunufactured using the killed, whole cell of a bacterium. The pertussis (whooping cough) part of the DTwP vaccine uses killed, whole cells of the pertussis bacterium. It works well for babies but it causes a higher rate of mild reactions in older children (see DTwP).

Non-encapsulated

Bacterium without a sugar coat.

Oedema

An abnormal accumulation of fluid in the body tissues.

Osteomyelitis

Inflammation of the bone.

Otitis media

Inflammation of the middle ear, usually due to viral or bacterial infection.

Pertussis (whooping cough)

Whooping cough is a disease that can cause long bouts of coughing and choking which can make it hard to breathe. It can last for up to 10 weeks. It is not usually serious in older children, but it can be very serious in babies under 1 year old.

Pharynx

The passage connecting the back of the mouth and nose to the opening of the tube leading to the stomach (oesophagus).

Pneumonia

Inflammation of the lung.

Safety

Vaccine safety is a measure of adverse reactions that a vaccine may cause.

Sinuses

The air-filled cavities in the bones behind the nose and cheeks.

Suppurative otitis media

Inflammation of the middle ear leading to the formation of pus.

Tetanus

Tetanus is a painful disease that affects the muscles and can cause breathing problems. It is caused by bacteria that are found in soil and manure and can get into the body through open cuts or burns. Tetanus affects the nervous system and, if it is not treated, it can kill.

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References

1 Plotkin SA and Orenstein WA. (Eds) Vaccines, (Third Edition) 1999. WB Saunders Company, Philadelphia. Ford FR. Diseases of the nervous system in infancy, childhood and adolescence (Sixth Edition). Springfield IL, Thomas CC. 1973, pp716-21. 3 Chin J. (Editor) Control of communicable diseases manual (Seventeenth Edition) 2000. American Public Health Association. Millard AH. Local tetanus. Lancet 1954; 2: 844-6. Wassilak SG, Orenstein WA and Sutter RW. Tetanus toxoid in Plotkin SA and Orenstein WA. (Eds) Vaccines (Third Edition), WB Saunders Company, 1999, pp441-74. Galbraith NS, Forbes P and Tillett H. National surveillance of tetanus in England and Wales 1930­79, Journal of Infection, 1981; 3: 181­91. Rushdy AA, White JM, Ramsay ME and Crowcroft NS. Tetanus in England and Wales 1984-2000. (in press) Cherry JD. The epidemiology of pertussis and pertussis immunization in the United Kingdom and the United States: a comparative study, Current Problems in Pediatrics, 1984; XIV(2): 1­78. Johnston IDA, Bland JM, Ingram D et al. Effect of whooping cough in infancy on subsequent lung functions and bronchial reactivity. American Review of Respiratory Disease 1986; 134: 270-5. 12 World Health Organisation. The Vaccine Assessment and Monitoring Team of the Department of Vaccines and Biologicals. Pertussis surveillance: a global meeting Geneva, 16-18 October 2000. 2001. 13 Miller E, Fleming DM, Ashworth LAE, Mabbett DA, Vurdien JE and Elliott TSJ. Serological evidence of pertussis in patients presenting with cough in general practice in Birmingham, Communicable Disease and Public Health, 2000; 3(2): 132­4. 14 Crowcroft NS and Britto J. Whooping cough ­ a continuing problem. BMJ 2002; 324: 1537-8. 15 Crowcroft NS, Andrews N, Rooney C, Brisson M and Miller E. Deaths from pertussis are underestimated in England. Archives of Disease in Childhood 2002; 88: 336-8. 16 Crowcroft NS, Spicer L, Tzivra O, Fry N, Harrison T, Maple C, Mok Q, Britto J, French A, Booy R and Miller E. Pertussis is under-estimated in infants admitted to paediatric intensive care units and wards in London. European Society for Paediatric Infectious Diseases (ESPID) 2001 Conference Abstracts, 10. 2001. 17 Crowcroft NS, Booy R, Harrison T, Spicer L, Britto J, Mok Q, Heath P, Murdoch I, Zambon M, George R and Miller E. Severe and unrecognised pertussis in UK infants. Archives of Disease in Childhood 2003 (in press) 18 Van Buynder PG, Owen D, Vurdein JE, Andrews NJ, Matthews RC and Miller E. Bordetella pertussis surveillance in England and Wales: 1995­97, Epidemiology and Infection, 1999; 123: 403­11. 19 Pollock TM, Miller E, Lobb JM and Smith G. Efficacy of pertussis vaccination in England. Report from the PHLS Epidemiological Research Laboratory and 21 area health authorities. BMJ, 1982; 285: 357-35 20 Pollock TM et al. Symptoms after primary immunisation with DTP and DT vaccine. Lancet July 21,1984: 146-9.

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4 5

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10 Department of Health and Social Security, Committee on Safety of Medicines and Joint Committee on Vaccination and Immunisation. Whooping cough. London, Her Majesty's Stationery Office, 1981. 11 Centers for Disease Control (CDC). Pertussis ­ United States, January 1992­June 1995, Journal of the American Medical Association,1995; 274(6): 450­1.

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21 Cody CL, Baraff LJ, Cherry JD et al. Nature and rates of adverse reactions associated with DTP and DT immunisations in infants and children. Paediatrics 1981; 68: 650-60 22 Farrington P, Pugh S, Colville A, Flower A et al. A new method for active surveillance of adverse reactions from diphtheria/tetanus/ pertussis and measles/mumps/rubella vaccines. Lancet 1995; 345: 567-9. 23 Miller E. Collapse reactions after whole cell pertussis vaccination. BMJ 1998; 316: 876. 24 Vermeer-de Bondt PE et al. Rate of recurrent collapse after vaccination with whole cell pertussis vaccine: follow-up study. BMJ, 1998; 316: 902-3. 25 Barlow W, Davis RL, Glasser JW, Rhodes PH et al. The risk of seizures after receipt of wholecell pertussis or measles, mumps and rubella vaccine. New England Journal of Medicine 2001; 345: 656-61. 26 Salisbury DM and Begg NT. (Eds) 1996 Immunisation against Infectious Disease. Department of Health, Welsh Office, Scottish Office Department of Health, DHSS (Northern Ireland). HMSO . 27 Gold M, Goodwin H, Botham S, Burgess M, Nash M, and Kempe A. Re-vaccination of 421 children with a past history of an adverse vaccine reaction in a special immunisation service. Archives of Disease in Childhood 2000; 83: 128-31. 28 Baron S, N'jamkepo E, Grimprel E et al. Epidemiology of pertussis in French hospitals in 1993 and 1994: 30 years after routine use of vaccination, Pediatric Infectious Disease Journal, 1998; 17: 412­18. 29 Offit PA, Quarlest J, Gerber MA, Hackett CJ, Marcuse EK, Kollman TR, Gellin BG and Landry S. Addressing parents' concerns: Do multiple vaccines overwhelm or weaken the infant's immune system? Pediatrics 2002; 109(1): 124-9.

30 Statement from the Committee on Safety of Medicines ­ Further data support safety of thiomersal in vaccines. Feb 2003 (www.mca.gov.uk/whatsnew/thiomersal statement_210203.pdf). 31 Pichichero ME, Cernichiari E, Lopreiato J et al. Mercury concentrations and metabolism Lancet November 2002, 360: 1737-41. 32 Magos L. Review on toxicity of ethyl mercury, including its presence as a preservative in biological and pharmaceutical products. Journal of Applied Toxicology 2001; 21: 1-5. 33 Ramsay ME et al. Adverse events and antibody response to accelerated immunisation in term and preterm infants. Archives of Disease in Childhood 1995; 72: 230-2. 34 Miller E. Overview of recent clinical trials of acellular pertussis vaccines. Biologicals 1999; 27: 79-86. 35 Howson CP, Howe CJ and Fineberg HV. (Eds) Adverse effects of pertussis and rubella vaccines: a report of the committee to review the adverse consequences of pertussis and rubella vaccines. Institute of Medicine. National Academy Press, Washington DC 1991. 36 Immunization Safety Review: Vaccinations and sudden unexpected death in infancy. 2003. Institute of Medicine. National Academy Press, Washington DC. 37 Fleming PJ, Blair PS, Platt MW, Tripp J, Smith IJ and Golding J. The UK accelerated immunisation programme and sudden unexpected death in infancy: case-control study. BMJ 2001; 322: 822. 38 Mitchell EA, Stewart AW and Clements M. Immunisation and the sudden infant death syndrome. New Zealand Cot Death Study Group. Archives of Disease in Childhood 1995; 73: 498-501. 39 Freed GL, Katz SL and Clark SJ. Safety of vaccinations: Miss America, the media and public health. Journal of the American Medical Association, 1996; 276(23): 1869-72.

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40 Golden GS. Pertussis vaccine and injury to the brain. J Pediatr 1990; 116: 854-61. 41 Griffith AH. Permanent brain damage and pertussis vaccination: is the end of the saga in sight? Vaccine 1989; 7: 199-210. 42 Bedford H and Elliman D. Childhood immunisation: a review for parents and carers. Health Education Authority, 1998. 43 Baraff LJ et al. Infants and children with convulsions and hypotonic-hyporesponsive episodes following DTP immunisation: follow-up evaluation. Pediatrics 1988; 81(6): 789-94. 44 Butler NR and Golding J. From birth to five: a study of the health and behaviour of Britain's five year olds. Oxford: Pergamon Press 1986. 45 Bellman MH, Ross EM and Miller DM. Infantile spasms and pertussis immunisation. Lancet 1983; i: 1031. 46 Goodman M, Lamm SH and Bellman H. Temporal relationship modelling: DTP or DT immunizations and infantile spasms. Vaccine 1998; 16(2/3): 225-31. 47 Odent MR, Culpin EE and Kimmel T. Pertussis vaccination and asthma: is there a link? Journal of the American Medical Association, 1994; 272: 592-3. 48 Kemp T et al. Is infant immunisation a risk factor for childhood asthma or allergy? Epidemiology 1997; 8: 678-80. 49 Nilsson L and Storsaeter J. Lack of association between pertussis vaccination and symptoms of asthma and allergy. Journal of the American Medical Association, 1996; 275(10): 760. 50 DeStefano F, Gu D, Kramaz P, Truman BI et al. Childhood vaccinations and risk of asthma. 2002; 21: 498-504. 51 Nuss RC, Eavey RD and Evans G. Hearing loss not associated with DTP vaccination or fever. Pediatrics 1993; 92: 740.

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© Crown Copyright 2003. Reproduced by the Health Promotion Agency for Northern Ireland on behalf of the Department of Health, Social Services and Public Safety with permission from the Department of Health.

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