Populations of persons who must be vaccinated with priority.

During a major pandemic of influenza, it would be impossible to vaccinate the entire population. Thus, it is necessary to determine which groups of individuals must be immunized with priority, considering the additional constraints related to the actual situation: to seek to reduce transmission of the virus and to maintain the activity of the community, especially those involved in public services. Another unavoidable factor must also be taken into consideration: the capacity for manufacturing and distributing the vaccine on an emergency basis. Lastly, contingency and planning measures must be made to avoid having to improvise.