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Statement on pertussis immunization

Canadian Medical Association Journal 1993; 149: 1132-1134
Health Canada, 1993
Reproduced with permission of the Minister of Supply and Services Canada, 1996

Copies of the original report (Canada Communicable Disease Report 1993; 19: 41-45) can be obtained from Eleanor Paulson, editor, CCDR, Bureau of Communicable Disease Epidemiology, Laboratory Centre for Disease Control, Tunney's Pasture, Ottawa, ON K1A 0L2.

The following recommendations on pertussis vaccine from the National Advisory Committee on Immunization will appear in the fourth edition of the Canadian Immunization Guide, scheduled for publication in autumn 1993. These revised recommendations represent a major change in vaccine usage and take account of the current understanding of adverse events associated with use of pertussis vaccine. Most adverse events are no longer contraindications to further immunization; only anaphylactic reaction to a previous dose remains an absolute contraindication to pertussis immunization. Other adverse reactions for which there are no sequelae or that have not been proven to be caused by the vaccine are no longer considered valid reasons for withholding immunization. It is hoped that simplification of the contraindications will improve vaccine utilization and achieve higher levels of age-appropriate immunization.

Contents

• Introduction
• Preparations used for vaccination
• Recommended usage
• Adverse reactions
• Contraindications and precautions
• Conditions no longer considered contraindications to pertussis vaccine
• References

Introduction

Pertussis (whooping cough) is a highly communicable bacterial disease caused by Bordetella pertussis. Because severity and fatality are greatest in infancy,[1] protective measures such as vaccination should be initiated as early in life as possible. Infants born to apparently immune mothers are highly susceptible to infection, particularly if maternal immunity was vaccine induced.[2,3]

During the last 30 years, vaccination has been widely practised, and the incidence and mortality from pertussis in Canada have declined remarkably.[4] However, outbreaks of pertussis continue to occur across Canada.[5,6] Over the past 5 years, the annual number of reported cases has ranged from just over 1000 to more than 8000. These figures likely underrepresent the true incidence of pertussis because of incomplete reporting.[7,8] Deaths and brain damage still occur from pertussis, particularly in young infants who have not been vaccinated.

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Preparations used for vaccination

Pertussis vaccine is a suspension of killed B. pertussis organisms prepared from strains belonging to the commonly occurring serotypes. Acellular pertussis vaccines are not yet available in Canada.

Pertussis vaccine is usually given combined with other agents, either adsorbed diphtheria and tetanus toxoids (DPT vaccine), adsorbed diphtheria and tetanus toxoids plus inactivated polio vaccine (DPT-polio vaccine) or Haemophilus influenzae type b conjugate vaccine. It is also available as a single non-adsorbed preparation.

In combined vaccines, the pertussis component potentiates the antibody response to the polio, diphtheria and tetanus antigens.[9]

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Recommended usage

Primary immunization consists of four doses of vaccine, usually given as a combined preparation (DPT or DPT-polio vaccine). The first three doses are given at intervals of 4 to 8 weeks beginning at 2 months of age, and the fourth dose 6 to 12 months after the third. A single booster dose is given to children of 4 to 6 years.

The dosage and route of administration should be as recommended by the manufacturer. Adsorbed vaccines are given intramuscularly. It is important that pertussis vaccination begin and be completed on time to ensure the greatest possible protection to the young infant, in whom the disease can be very serious. Because the incidence and severity of the disease greatly decrease with age, and because adverse reactions may be more common in older children and adults, pertussis immunization is not generally recommended for persons 7 years of age or older. However, older children and adults who have pertussis are an important source of infection for young infants.[10] For this reason, adult immunization with pertussis vaccine may be recommended in the future when acellular pertussis vaccines become available.

Protection against infection is estimated to be 60% to 80%; protection against severe disease is 85% or higher.[11,12] Protection against disease afforded by the vaccine decreases as the time interval since vaccination increases.[13] If pertussis occurs in infants and children who have received three or more doses of vaccine, it is almost always mild and serious complications are rare.[7,14]

Infection in vaccinated persons may cause bronchitis without typical "whooping." Illnesses clinically indistinguishable from whooping cough can be caused by other respiratory pathogens, including other Bordetella species,[15] and may lead to a false assumption of ineffectiveness of the pertussis vaccine.

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Adverse reactions

Pertussis vaccine is usually administered in combination with diphtheria and tetanus toxoids; it is responsible for most of the reactions to DPT vaccine.[16] Minor local reactions such as transient pain, redness and swelling and systemic symptoms such as fever and fussiness occur in 50% to 75% of vaccine recipients but are self-limited. Drowsiness and anorexia are also common. The incidence and severity of fever and irritability can be significantly reduced by administration of acetaminophen (15 mg/kg per dose) at the time of inoculation and again 4 and 8 hours after vaccination.[17,18] Reducing the temperature may also minimize the occurrence of febrile convulsions. Hence acetaminophen prophylaxis is particularly recommended for children with a personal or family history of convulsions.

Persistent, inconsolable crying lasting 3 or more hours (in 1% of cases) and high-pitched, unusual screaming (in 0.1%) have also been reported after pertussis vaccination. Convulsions and a hypotonic-hypo-responsive state have each been reported to occur at a frequency of about 1:1750 injections of DPT vaccine.[16] Most convulsions are brief, generalized and self-limited and are usually associated with fever. Neither febrile nor afebrile convulsions have been shown to be associated with a subsequent seizure disorder.[19] Complete recovery has been observed, without persistent neurologic or developmental defects, on follow-up of children with hypotonic-hyporesponsive episodes or convulsions.[20]

Although there has been a concern about the possible association between pertussis vaccine and severe neurologic illness (including encephalopathy) occurring within 72 hours of vaccination in previously healthy infants, the risk of an association is so small compared to the background rate for these types of events that the question of causation probably cannot be answered.[21,22] The majority of such illnesses observed in the National Childhood Encephalopathy Study (NCES) in the United Kingdom were prolonged and/or complex convulsions. All such children were normal on follow-up 12 to 18 months later. Reanalysis of the NCES data has failed to confirm that there was an increased risk of permanent brain damage following acute neurologic illness occurring within 7 days of pertussis vaccination.[23] Additional studies have also failed to demonstrate an association between pertussis vaccine and permanent neurologic sequelae.[24]

In comparisons of adverse effects occurring after receipt of DPT vaccine with those following receipt of diphtheria-tetanus (DT) vaccine, minor local reactions have been reported in about 60% of DPT recipients compared with 10% of those given DT; fever was seen in 46% given DPT compared to 10% given DT; drowsiness in 31% receiving DPT compared to 15% following DT; and persistent crying in 3% given DPT but less than 1% of those given DT.[16]

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Contraindications and precautions

Absolute

Pertussis vaccine should not be given to individuals who have had an anaphylactic reaction to a previous dose. Because these events are so rare, it is not known which component of the combined DPT vaccine is responsible for the allergic reaction. Therefore, no further doses of any of the DPT components should be given unless assessment implicates the responsible antigen.

Relative

No long-term sequelae have been associated with hypotonic-hyporesponsive episodes; however, since their pathogenesis is unknown, it may be prudent in areas of low pertussis incidence to withhold the pertussis component and continue vaccination with DT. Children who have had one of these episodes with a previous pertussis vaccine dose can continue to receive pertussis vaccine if the incidence of the disease is high in their area.

Deferral

Deferral of pertussis vaccination may be considered in children with a progressive, evolving or unstable neurologic condition in order to prevent confusion of the diagnosis if an adverse event occurs. Such conditions include tuberous sclerosis, hypoxic encephalopathy secondary to prematurity, poorly controlled convulsions, central nervous system malformations and neurodegenerative diseases. Continued deferral should be reassessed at each visit; pertussis vaccination should be reinstituted when the condition has resolved, been corrected or controlled.

When pertussis vaccine is contraindicated or deferred, vaccination with diphtheria and tetanus toxoids, when needed, can be continued using combined DT vaccine without a pertussis component. A plain pertussis vaccine is available for administration to infants whose pertussis vaccination was deferred.

Pertussis vaccine is not recommended routinely for persons 7 years of age or older. Children who have recovered from culture-proven pertussis do not need further vaccination with pertussis vaccine.

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Conditions no longer considered contraindications to pertussis vaccine

Certain other events temporally associated with pertussis vaccination are no longer considered contraindications.

• High temperature within 48 hours of vaccination indicates the likelihood of recurrence of fever with subsequent doses.[25] Febrile convulsions may be more likely in a susceptible child who has a high temperature. However, there are no long-term sequelae from these convulsions, and pertussis vaccination can continue. Acetaminophen prophylaxis reduces the incidence of fever and may reduce febrile convulsions temporally related to pertussis vaccination.
• Afebrile convulsions have not been shown to be caused by pertussis vaccine and are not a valid contraindication to pertussis vaccination.
• Persistent, inconsolable crying and an unusual high-pitched cry after pertussis vaccine also are not associated with any sequelae and may simply be a pain response at the site of injection in young infants.[26] These reactions do not preclude further pertussis vaccination.
• Onset of encephalopathy temporally related to pertussis vaccination does not indicate that the vaccine was the cause.[27] Encephalopathy itself from whatever cause is not a contraindication to pertussis vaccination but deferral may be considered until the neurologic condition is stable.

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References

1. Summary of notifiable diseases, United States, 1991. MMWR 1991; 40: 35-36, 57-63
2. Van Savage J, Decker MD, Edwards KM et al: Natural history of pertussis antibody in the infant and effect on vaccine response. J Infect Dis 1990; 161: 487-492
3. Bass JW, Zacher LL: Do newborn infants have passive immunity to pertussis? Pediatr Infect Dis J 1989; 8: 352-353
4. Pertussis incidence in Canada. Can Dis Wkly Rep 1985; 11: 33-35
5. Pertussis outbreak in the West Island Region of Montreal. Can Dis Wkly Rep 1990; 16: 107-110
6. Pertussis outbreak in the Yukon Territory -- 1989. Ibid: 63-67
7. Halperin SA, Bortolussi R, MacLean D et al: Persistence of pertussis in an immunized population: results of the Nova Scotia enhanced pertussis surveillance program. J Pediatr 1989; 115: 686-693
8. Sutter RW, Cochi SL: Pertussis hospitalizations and mortality in the United States, 1985-1988. Evaluation of the completeness of national reporting. JAMA 1992; 267: 386-391
9. Cherry JD, Brunell PA, Golden GS et al: Report of the task force on pertussis and pertussis immunization -- 1988. Pediatrics 1988; 81 (suppl, pt 2): 939-984
10. Nelson JD: The changing epidemiology of pertussis in young infants. The role of adults as reservoirs of infection. Am J Dis Child 1978; 132: 371-373
11. Blennow M, Olin P, Granström M et al: Protective efficacy of a whole cell pertussis vaccine. BMJ 1988; 296: 1570-1572
12. Onorato IM, Wassilak SG, Meade B: Efficacy of whole-cell pertussis vaccine in preschool children in the United States. JAMA 1992; 267: 2745-2749
13. Lambert HJ: Epidemiology of a small pertussis outbreak in Kent County, Michigan. Public Health Rep 1965; 80: 365-369
14. Fine PEM, Clarkson JA: Reflections on the efficacy of pertussis vaccines. Rev Infect Dis 1987; 9: 866-883
15. Geller RJ: The pertussis syndrome: a persistent problem. Pediatr Infect Dis J 1984; 3: 182-186
16. Cody CL, Baraff LJ, Cherry JD et al: Nature and rates of adverse reactions associated with DTP and DT immunizations in infants and children. Pediatrics 1981; 68: 650-659
17. Ipp MM, Gold R, Greenberg S et al: Acetaminophen prophylaxis of adverse reactions following vaccination of infants with diphtheria-pertussis-tetanus toxoids-polio vaccine. Pediatr Infect Dis J 1987; 6: 721-725
18. Lewis K, Cherry JD, Sachs MH et al: The effect of prophylactic acetaminophen administration on reactions to DTP vaccination. Am J Dis Child 1988; 142: 62-65
19. Shields WD, Nielsen C, Buch D et al: Relationship of pertussis immunization to the onset of neurologic disorders: a retrospective epidemiologic study. J Pediatr 1988; 113: 801-805
20. Baraff LJ, Shields WD, Beckwith L et al: Infants and children with convulsions and hypotonic-hyporesponsive episodes following diphtheria-tetanus-pertussis immunization: follow-up evaluation. Pediatrics 1988; 81: 789-794
21. Marcuse EK, Wentz KR: The NCES reconsidered: summary of a 1989 workshop. Vaccine 1990; 8: 531-535
22. Howson CP, Howe CJ, 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, Natl Acad Pr, Washington, 1991
23. Wentz KR, Marcuse EK: Diphtheria-tetanus-pertussis vaccine and serious neurologic illness: an updated review of the epidemiologic evidence. Pediatrics 1991; 87: 287-297
24. Griffin MR, Ray WA, Mortimer EA et al: Risk of seizures and encephalopathy after immunization with the diphtheria-tetanus-pertussis vaccine. JAMA 1990; 263: 1641-1645
25. Baraff LJ, Cody CL, Cherry JD: DTP-associated reactions: an analysis by injection site, manufacturer, prior reactions, and dose. Pediatrics 1984; 73: 31-36
26. Long SS, Deforest A, Pennridge Pediatric Associates et al: Longitudinal study of adverse reactions following diphtheria-tetanus-pertussis vaccine in infancy. Pediatrics 1990; 85: 294-302
27. Camfield P: Brain damage from pertussis immunization. Am J Dis Child 1992; 146: 327-331

Source: The National Advisory Committee on Immunization.

Disclaimer

This guideline is for reference and education only and is not intended to be a substitute for the advice of an appropriate health care professional or for independent research and judgement. The CMA relies on the source of the CPG to provide updates and to notify us if the guideline becomes outdated. The CMA assumes no responsibility or liability arising from any outdated information or from any error in or omission from the guideline or from the use of any information contained in it.

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