[Table of Contents]

Volume: 25S5 - August 1999

Proceedings of the National Varicella Consensus Conference
Montreal, Quebec
May 5-7, 1999

Introduction

The National Varicella Consensus Conference was sponsored by the Laboratory Centre for Disease Control (LCDC), Health Canada, and held from May 5-7, 1999, in Montreal, Quebec. The first varicella vaccine in Canada, a live attenuated Oka strain vaccine, was licensed in December 1998 and is recommended by the National Advisory Committee on Immunization (NACI) for primary immunization of healthy persons aged >= 12 months⁽¹⁾.

While varicella is often considered to be a fairly benign disease among otherwise healthy children aged up to 12 years, available epidemiologic data show that cases in that age group account for a substantial public health burden: approximately 90% of all varicella cases, 80% to 85% of varicella-associated physician visits, 85% to 90% of hospitalizations, nearly 50% of fatal cases, and the majority of annual costs, most of which are related to productivity losses by caregivers⁽¹⁾. In children aged < 10 years, varicella is now the main cause of death due to diseases potentially preventable by routine childhood vaccination in Canada.

Primary varicella is a more severe disease in adults, with a case fatality rate 10 to 30 times higher than in children. Moreover, in both adults and children, the majority who die of varicella have no identifiable risk factor for severe disease.

Currently, varicella vaccine is not universally accepted by all health care professionals or the public. Multiple competing priorities for public health resource allocation at the provincial/territorial or local level increase the likelihood that the timing of implementation of varicella vaccination programs will differ widely among provinces and territories. In addition, a number of logistic challenges to the implementation of routine vaccination programs exist with the currently licensed freezer-stable vaccine, which is the most heat-sensitive of all vaccine products currently available. The primary challenges are the cost of the vaccine, and the storage and handling requirements (specific issues include inadequate freezer capacity, cost of freezer space for both public health delivery and physicians' offices, and potential difficulties with the cold chain maintenance in the delivery of the vaccine to remote areas).

Modeling data suggest that unless high coverage with varicella vaccine is uniformly achieved in all jurisdictions, there is a danger of causing a shift in the epidemiology of varicella to the adult population with a resulting increase in morbidity. Thus, more than for any routinely used vaccine, the urgent need for national consensus on the potential benefits of routine varicella vaccination and the strategy for implementing routine vaccination programs was recognized.

The goal of the conference was to present a forum for federal, provincial, and territorial public health representatives, clinical experts, and other professional stakeholders to discuss and exchange ideas on issues related to the varicella vaccine, including implementation of population-based vaccination programs, provider and public acceptance of the vaccine, and ways to maximize the benefits of the vaccine for the Canadian population.

The specific objectives of the conference were to discuss and exchange ideas on

• national goals for the control of varicella and herpes zoster
• a coordinated approach to implementation of varicella vaccination programs in all provinces and territories
• post-marketing research needs for varicella-zoster virus (VZV)-related disease and varicella vaccine

The conference included broad participation from all major stakeholders identified: the Laboratory Centre for Disease Control, the Bureau of Biologics and Radiopharmaceuticals, Medical Services Branch, provinces and territories (chief medical officers of health, provincial/territorial epidemiologists, and local representatives), the Advisory Committee on Population Health, the Canadian Occupational Health Nurses Association, the Canadian Association of Medical Microbiologists, the Community Hospital Infection Control Association Canada, the Canadian Infectious Disease Society, the Canadian Nurses Association, the Canadian Paediatric Society, the Canadian Public Health Association, the College of Family Physicians of Canada, the National Advisory Committee on Immunization, the Society of Obstetricians and Gynaecologists of Canada, the Toronto Fetal Centre, the U.S. Centers for Disease Control and Prevention, and a consumer advocate.

As well, representatives of two vaccine manufacturing companies were invited to attend the conference as observers and to present the most current technical and scientific information on their respective products: Merck Frosst Canada's VARIVAX® (the only vaccine currently licensed in Canada) and SmithKline Beecham's Varilrix^TM (not currently licensed in Canada). A representative of the American Red Cross also participated as an observer.

Although representation was invited from the Canadian Blood Services and HémaQuébec, neither organization was able to send a representative to the conference. Manufacturer representatives were invited to sit in on all plenary sessions, but they did not participate in the plenary debate or in working group discussions, nor did they provide funding for the event. A request to exclude manufacturers from the plenary sessions was defeated by majority vote. A detailed list of participants is provided in Appendix A.

Conference Format and Process

The meeting began with a series of scientific presentations to the plenary group by invited experts from Canada and the United States (the invited speaker for the European perspective was unable to attend; however, written material was provided to participants). This was followed by 2 days of discussion in five concurrent working groups on specific public health issues and presentation of working group summaries to the plenary for discussion.

Current scientific information was presented on the following topics:

• Virology, clinical syndromes and immune response to VZV (Dr. Anne Gershon)
• Epidemiology of VZV in Canada (Dr. Barbara Law, Dr. Yves Robert, and Dr. Danuta Skowronski)
• Varicella seroprevalence in Canadian populations (Dr. Sam Ratnam)
• Risk and incidence of Group A beta hemolytic streptococcal infections in varicella (Dr. H. Dele Davies)
• Epidemiology and surveillance of VZV in the United States (Dr. Jane Seward)
• Epidemiologic modeling of varicella in Canada (Dr. Gaston de Serres, Mr. Marc Brisson)
• Surveillance needs for VZV and varicella vaccine in Canada (Dr. Monique Douville-Fradet)
• Infection control for VZV (Dr. Anne Matlow)
• Varicella vaccine experience in the United States (Dr. Jane Seward)
• Preventing varicella in special risk populations (Dr. Myron Levin)
• Economic analysis of varicella vaccine use in Canada (Dr. Jaime Caro)
• VARIVAX^® (Dr. Didier Reymond)
• Varilrix^TM (Dr. Alan Kimura)

To create a balance of perspectives and professional diversity, participants were assigned to one of five concurrent working groups. Participants were assured that divergent opinions were not only welcome but absolutely necessary to the process of consensus building. Each working group comprised 9 to 12 participants as well as a pre-assigned group chair and rapporteur (Appendix B). The five working groups discussed issues in the following content areas: (1) Public health goals and objectives for varicella control and vaccine coverage; (2) Development and implementation of varicella vaccination programs; (3) Varicella vaccine use in special populations; (4) Promotion of varicella vaccination programs; and (5) Surveillance needs (disease and vaccine related).

Working group participants were asked to deliberate on specific questions relating to their content area and to propose recommendations based on those questions. The proposed recommendations from each group were presented to the plenary for discussion in a process of consensus building, to arrive at final recommendations. Consensus was defined as agreement that a given recommendation under discussion was acceptable to participants. It was recognized that consensus did not require unanimity, although it would require more than a simple majority of voting participants in favour of a recommendation. Electronic key pads were used to record votes on each recommendation to ensure consistency, reliability, and voter confidentiality. The specific criteria used for reaching consensus on recommendations were:

• A vote of 90% to 100% in favour of a motion was considered as consensus on a given recommendation.
• A vote of 75% to 89% in favour of a motion was considered as consensus if there were no major objections expressed by participants; if an objection was raised, the recommendation was opened to further discussion.
• A vote of < 75% in favour of a motion resulted in further discussion of the recommendation and repeat voting.

The following section of this report presents the summary of the plenary discussions for each working group's proposals and the final consensus recommendations. The recommendations took into account current scientific knowledge presented at the conference as well as information presented to participants as background reading material before the meeting (Appendix C). Although the majority of participants were invited after being identified by various stakeholder groups, they did not necessarily express the views of the groups they belong to and may have expressed their personal views on some issues. In his opening remarks, Dr. Paul Gully, Deputy Director General, LCDC, noted that it would be important to evaluate the process of consensus by measuring the acceptance and implementation of the recommendations and guidelines from the consensus conference across the country.

[Previous] [Table of Contents] [Next]