National Consensus
Conference on Pertussis

[Table of Contents]

RECOMMENDATIONS 

Goals 

It was agreed that, given the information presented during the last 2 days, the goals of the pertussis control strategy, as formulated at the 1993 consensus conference, are inadequate for the present circumstances and should be changed to the following. 

1.  The goal of the pertussis control strategy is to decrease morbidity and mortality from pertussis across the entire life span. 

• Given the current state of knowledge, it is unclear whether elimination is achievable. 

2.  Protection of adolescents and adults is a worthy goal for the benefit of these cohorts themselves. 

• It is not clear whether a collateral benefit of protection of infants would be achieved. 

Priorities, Methods and Conditions 

3.  It is necessary to prioritize efforts to control disease in various cohorts. 

• Improve control in infants and young children. 
• Control pertussis in adolescents (by use of universal adolescent immunization). 
• Develop and implement effective strategies for control of pertussis in adults. 

4.  There is a priority to ensure that the pertussis immunization schedule maximizes safety, effectiveness and efficiency. 

• number of doses 
• interval between doses 

Factors that must be taken into account in making changes to the immunization schedule in order to improve pertussis control are the possible adverse events associated with multiple doses, the duration of immunity, other antigens given concurrently, the cost and logistics. 

If the primary dose were to be accelerated in order to protect infants at an earlier age, then the effect of this on other vaccines now given at the same time would need to be considered. The lack of a monovalent acellular pertussis vaccine limits the choices. The World Health Organization has a recommendation not to immunize until after the first month. 

Routine immunization of adolescents with the new adolescent form of acellular pertussis vaccine has been recommended by NACI. One possibility would be to provide the adolescent booster dose with the tetanus and diphtheria boosters, another would be to give it with hepatitis B vaccine. The best way of achieving pertussis control in adults, for instance through immunization of new parents, is a subject for research. 

Targets and Measurable Outcomes 

The difficulty in setting quantifiable targets for a cyclical disease like pertussis was acknowledged. 

5.  The ultimate target should be decreased disease outcome. 

• Improved surveillance may affect achievement of pertussis control outcomes. 
• Decrease the number of deaths from pertussis to zero. 
• Decrease rates of hospital and ICU admission among young infants. 

  • Precise targets and timing to be determined by future research, with the goal of having a strategy in place by 2008. 
• Reduce the reported incidence of pertussis among older children and adolescents to at least the levels present in preschool-aged children. 

6.  Process outcomes: immunization should be delivered on time. 

• At least 95% of infants should receive the first dose of pertussis vaccine before 3 months of age. 
• At least 95% of infants should receive two doses of pertussis vaccine by 5 months of age. 
• At least 95% of children should receive other recommended pertussis vaccine doses at the recommended age (within 3 months). 

Laboratory Diagnosis 

7.  Polymerase chain reaction (PCR) should be established as the new gold standard for diagnosis within 3 years. 

• Two sets of primers should be used. 
• External proficiency testing should be in place to ensure quality control. 

8.  A system should be established for selective performance of culture for strain typing, antibiotic sensitivity testing, and identification of Bordetella parapertussis and B. holmseii. 

9.  There should be support for the development of criteria for serologic diagnosis. 

10.  International reference sera and reference antigens should be available. 

11.  An international consensus conference on pertussis diagnostic methods should be held. 

• PCR 
• serology 
• pulsed-field gel electrophoresis 
• specimen collection, handling and transport 

Surveillance 

Surveillance was defined as follows: 

The timely collection, analysis and dissemination of information that leads to public health action and/or hypothesis generation. 

General 

12.  Data fields submitted nationally should be standardized and applied consistently across Canada (i.e. there should be harmonization). 

• Required parameters are age, sex, onset, outcome, method of confirmation, clinical presentation. 
• Ideally, there should also be information on vaccine status. 

13.  Data fields should be specific enough to allow valid and useful analysis and interpretation. 

• i.e. non-aggregated age information in years and/or months 

14.  Support for infrastructure for local public health is required in order to ensure that there is adequate case investigation and data entry. 

15.  Linked disease and vaccine registries are a priority for development and implementation (e.g. to connect with individual level vaccine status). 

Routine Disease-related Surveillance 

The purpose of routine disease surveillance is to monitor age-related trends in incidence, morbidity and mortality and to permit outbreak recognition. 

16.  Pertussis should be notifiable in all provinces and territories by both laboratories and clinicians. 

17.  The 2000 revised case definition^*  should be adopted, except for reporting of only laboratory confirmed cases (see next item). 

18.  National reporting of pertussis should be of clinical and confirmed cases, with an indication of the method of confirmation. 

19.  The case definition should be revised to include approved laboratory methods that have been validated and standardized as developed. 

20.  Intermittent statistical review of hospitalization and mortality data should be carried out routinely. 

21.  IMPACT (Immunization Monitoring Program - Active) should be recognized and supported as an important component of routine pertussis surveillance. 

Routine Vaccine-related Surveillance 

22.  A system for accurately monitoring annual vaccine coverage should be established and maintained in each jurisdiction. 

• minimum at 24 months and other ages specified in the objectives 
• additional age groups to be added according to changes in vaccine schedule 

23.  Standards and data fields for assessing vaccine status should be developed and applied consistently across Canada (e.g. What does “up to date” mean?) 

24.  IMPACT surveillance and routine vaccine-associated adverse event reporting on a timely basis should be maintained to effectively monitor vaccine safety and ensure public confidence. 

Special Disease-related Surveillance 

25.  Active surveillance initiatives should be established in selected jurisdictions to assess the duration and effectiveness of the entire pertussis immunization program (including the new adolescent program). 

26.  Surveys or enhanced surveillance projects should be conducted to calibrate the sensitivity of the passive surveillance system. 

27.  Enhanced surveillance projects should be implemented to assess the impact and consequences of pertussis in adults and adolescents. 

28.  Periodic enhanced mortality tracking from multiple sources should be implemented to better gauge this indicator (e.g. using capture-recapture methods). 

29.  All undiagnosed deaths in infants and SIDS (sudden infant death syndrome) cases should be investigated for pertussis. 

30.  Circulating/outbreak strains should be characterized to monitor the evolution of the organism. 

31.  Special studies should be established to assess particular vaccine-related risks in adolescents and adults (e.g. to monitor injection site reactions) and the cumulative effect of multiple doses. 

32.  An initiative to monitor knowledge, attitudes and beliefs among members of the public and health care workers should be established both before and after the introduction of an adolescent/adult program, related to 

• pertussis disease 
• immunization against pertussis 

Treatment and Prophylaxis 

Treatment 

33.  Any of the following should be used for treatment of pertussis: 

• azithromycin 10 mg/kg once daily for 1 day and then 5 mg/kg once daily for 4 days 
• clarithromycin 15 mg/kg twice daily in a divided dose for 7 days 
• erythromycin 40 mg/kg three times daily in a divided dose for 7 days 
• choice based on cost, side effects, etc. 

34.  Antibiotics should be administered as soon as possible after onset of illness; there is no limit to the start date for treatment of symptomatic, untreated cases of pertussis whose culture or PCR results are positive. 

35.  Patients should no longer be considered infectious after 5 days of therapy. 

36.  Infants < 2 months of age who are receiving macrolide antibiotics should be monitored for symptoms and signs of pyloric stenosis. 

Chemoprophylaxis 

37.  For confirmed cases (culture, PCR, serology or epidemiologic link) or clinically diagnosed cases occurring during an outbreak, chemoprophylaxis should be given to the following: 

• household contacts (including attendees at family day care centres) where there is a vulnerable person (an infant < 1 year of age [vaccinated or not] or a pregnant woman in the third trimester) 
• for out of household exposures, vulnerable individuals who have had face-to-face exposure and/or have shared confined air for > 1 hour 

38.  For chemoprophylaxis, the same antimicrobials and schedule should be used as outlined under Treatment. 

39.  When used, chemoprophylaxis should be implemented as soon as possible. 

• Efficacy is related to early implementation and is unlikely to be of any benefit after 21 days have elapsed since the first contact. 

40.  Antibiotics recommended for the control of pertussis where household chemoprophylaxis is indicated (index cases, household contacts) should be supplied by public health. 

Notification and Early Treatment 

41.  There should be notification (see Appendix 1 for notification procedures) of other contacts of confirmed cases in the following settings: 

• other households 
• non-family day care centres 
• schools 
• health care settings 
• work places 

42.  Treatment should be based on symptoms suggestive of early pertussis (coryzal stage). 

43.  The same antibiotics and schedule should be used as outlined under Treatment. 

44.  The settings listed in recommendation 41 should be assessed for special circumstances that might warrant chemoprophylaxis. 

Outbreak Management 

45.  If there is a confirmed case in a household the following apply: 

• vaccination is not recommended for outbreak management, but the opportunity should be taken to update the immunization status of contacts if required. 
• exclusion is not a proven effective strategy; however, in high risk situations (where there are vulnerable individuals - for instance, infants) exclusion until 5 days after the start of antibiotic therapy or, if no treatment is given, until after 21 days and with negative results from culture or PCR should be at the discretion of the medical officer of health. 

46.  If there are two or more confirmed cases epidemiologically linked in a non-household setting (school, day care centre without infants < 1 year old) the following apply: 

• Chemoprophylaxis is not indicated. 
  • In household-like settings use individual judgement. 
  • Alert parents to signs and symptoms of pertussis so that early diagnosis and treatment can be initiated when needed; inform community physicians of increased pertussis activity. 
• Use the opportunity to update routinely scheduled immunizations in school or day care contacts as required. 
  • Catch up immunization of other cohorts can be considered by public health authorities. 
  • All parents of contacts should be notified of the possibility of purchasing vaccine from the family physician. 
• Exclusion criteria are the same as in recommendation 45. 

47.  Public health nurses should obtain training and gain expertise in taking nasopharyngeal swabs. 

Research Agenda 

Topics to be included on the research agenda are as follows. 

• Evaluation of each change recommended by this consensus conference upon implementation. 
• Assessment of the population effectiveness of such strategies as immunization of new mothers, immunization of household contacts of a newborn, immunization of other close contacts of a newborn. 
• Methods to reduce mortality and morbidity (hospitalization) in young infants. 
• Use of acellular pertussis vaccine in outbreak control. 
• Schedule issues 
  • 5^th dose 
  • primary series 
  • accelerated schedules 
  • newborn immunization 
• Efficacy of vaccine in adolescents (and adults) 
• This should not delay implementation. 
• Seroepidemiology in new Canadian adolescents. 
• Evaluation of single dose of azithromycin. 
• Monitoring of macrolide resistance. 
• Duration of protection of children fully immunized with acellular vaccine. 
• Cost-effectiveness of different strategies. 
• Investigation of the point at which patients receiving treatment are no longer infectious. 
• Source of infection of young infants. 
• Mechanisms of transmission related to 
• culture/PCR positive results 
• symptoms 
• Effect of maternal immunization on infant disease. 
• Immunization during pregnancy. 
• Role of maternal antibody (transplacental and via breast milk) in the protection of infants in the first few months of life. 
• The effect of the interval between booster immunization and childbirth on the production of antibody titres that do or do not protect infants. 

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