Pan-canadian public health network council report and policy recommendations on the use of antivirals for prophylaxis during an influenza pandemic

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Process For Recommendation Development

1. Background and Assumptions

In the context of an actual influenza pandemic, the immediate focus would be on mitigating its impact, through implementation of pandemic plans adapted to the specific type of pandemic faced. Current planning assumptions include: pandemic activity of moderate severity in Canada, origin of the pandemic strain outside of Canada; and that the pandemic virus would be consistent with seasonal influenza in terms of high risk groups and epidemiologic parameters, such as incubation period.

Integral components of the health response to an influenza pandemic are: early identification and treatment of cases; implementing public health measures; sustaining the critical infrastructure sectors, including the health care system, through implementation of business continuity plans; and, at some point, implementation of a pandemic influenza immunization program. TGAP assumed that the recommended antiviral prophylaxis policy would be framed as a population-based approach, in which measures would be implemented by public health authorities, in collaboration with the clinical care, emergency response, and private sectors as required.

It is assumed that all the considerations evaluated by TGAP would be subject to ongoing monitoring and, therefore, the assumptions underlying these recommendations would be reassessed as new evidence arises, and at the time of a pandemic, with modification of response plans as needed.

2. Synthesis of Considerations

TGAP’s extensive deliberations on all key considerations enabled the identification of the issues fundamental to a government decision on the provision of antivirals for prophylaxis. It is suggested that the recommendations and policy should:

• address the goals of the Antiviral Strategy, and implicitly those of the CPIP;
• be based on sound evidence – including that related to efficacy, potential effectiveness, safety, potential for antiviral resistance, and potential for impact at a population level;
• be practical, possible, reasonable and rational – therefore not wasteful of drugs or human resources;
• be a “considered liability” – address the feasibility of comprehensive, just, fair and equitable implementation of the policy recommendations, consider existing standards of practice on the use of antivirals for prophylaxis in Canada and Canadian indications for use of the drugs;
• be affordable and consider opportunity costs;
• include consideration of international benchmarking;
• be transparent - a key to acceptance by target groups, stakeholders and citizens;
• ensure prudent approach to population-based use of antivirals for prophylaxis; and
• promote consistency across the country.

3. Potential Target Groups for Antiviral Prophylaxis

In the event that TGAP were was to recommend the acquisition and use of antivirals for prophylaxis during a pandemic, it also was asked to identify target groups for whom governments might consider the purchase of prophylactic antivirals.

Previous planning guidance in the form of a priority list for antiviral indications during a pandemic provided some foundation for this work. However, it was developed in the absence of a National Antiviral Stockpile, prior to the decision to focus on antiviral treatment and without consideration of how antivirals might be used strategically in combination with public health measures and immunization. It was determined that a fresh look at potential prophylactic indications was necessary, with consideration of their potential contribution to a comprehensive pandemic strategy. TGAP sought to provide this perspective based not only on a review of scientific considerations, but also on analysis of all of the previously described considerations with a focus on those fundamental to government decision-making.

Selection Criteria

The initial consideration, of making prophylaxis available to the entire population, was dismissed early in the process as a potentially very inefficient strategy because:

1. it would require a high investment of public funds on an ongoing basis;
2. there are both scientific and logistical challenges that could significantly impact the theoretical effectiveness of this type of strategy when applied at the population level;
3. there is a potentially steep opportunity cost of embarking on such a strategy;
4. such a strategy is not being considered in other countries; and
5. early treatment will be available in Canada to those who, based on medical grounds, need and are expected to benefit from antiviral treatment.

TGAP built on work done by PIC and the Antivirals Working Group in identifying specific groups for whom prophylaxis would be expected to contribute the most toward meeting the goals of the CPIP. These groups included health care workers, other critical infrastructure workers, those at high risk of poor outcome of pandemic influenza and those residing in health care institutions.

TGAP also considered other groups suggested during the deliberative dialogues. These included teachers, day-care workers and others whose absenteeism or inability to work could disrupt the functioning of society at large, and the families of these workers, as well as First Nations and Inuit who as a group might be expected to be at high risk of poor outcomes of pandemic influenza.

a) Quantitative Analysis

Rather than aiming to offer a definitive list of who should and who should not receive antivirals for prophylaxis, TGAP attempted to identify criteria against which it could judge who might be considered for antivirals for prophylaxis. The initial approach to selection and prioritization using the criteria attempted to assign scores, ratings, or weightings to proposed target groups and the criteria.

The criteria were grouped into sets as follows:

1. Goals - the group or individuals’ contribution to meeting the goals of the CPIP;
2. Logistics, including ease of identifying, locating and reaching members of a potential target group;
3. Standards, such as current standards of practice, approved use, international trends and public opinion;
4. Scientific evidence, including clinical trial data, indicators of effectiveness, and considerations regarding efficiency.

An attempt to systematically use a scoring system to apply the criteria to the proposed target groups proved to be a highly complex task. It was determined that the development of a system which could be workable, reliable and consistently applied could not be completed in the time frame of this Report. The discussion also demonstrated the large amount of work required to establish, for instance, who in the critical infrastructure sectors could be considered the most critical. Finalizing operational decisions would be difficult without full knowledge of group size, composition, and job descriptions at the operational or field level. Input and information from these groups, which are primarily in the private sector, should be sought to provide sufficient data for the development of effective operational guidelines.

b) Qualitative Approach

TGAP ultimately took an alternative approach to the development of recommendations, in light of the challenges with the quantitative approach. The recommendations were the subject of much debate and careful examination of definitions, understanding of terminology, and examination of issues as they relate to Canadian society and values, as well as to those delivering health care.

The review of definitional terms served to ensure that TGAP members shared a common understanding of the potential uses of antivirals, whether for treatment or prophylaxis, as well as the differences between pre- and post-exposure prophylaxis.

There was careful consideration of how, for whom, and why antivirals should or should not be stockpiled by governments and used for prophylaxis during different phases of a pandemic. These deliberations resulted in recommendations explaining the context, rationale, and strengths and weaknesses of each recommendation.

4. Uses of Antivirals during an Influenza Pandemic

TGAP limited its discussion to the World Health Organization’s (WHO) Pandemic Phases 4, 5 and 6 (see Annex 4), which covers the period from the identification of the first cases with human-to-human transmission in Canada, to the overall spread of the novel or pandemic virus in Canada. The policy decision to set the size of the NAS for early treatment of cases at 55 million doses assumed that this would be sufficient to treat the proportion of cases that, based on medical grounds, are determined to need and are expected to benefit from antiviral treatment. However, recognizing that operational plans for the implementation of the treatment strategy have not been completed in many jurisdictions, TGAP has included one aspect of early treatment in its recommendation for use of antivirals during an influenza pandemic.

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