Are presently available vaccines useful in averting an influenza pandemic?
– Yes, but in a precisely targeted way. Current vaccines, when administered to high-risk groups, such as poultry cullers, protect against circulating human strains and thus reduce the risk that humans at high risk of exposure to the bird virus might become infected with human and avian viruses at the same time. Such dual infections give the avian and human viruses an opportunity to exchange genes, possibly resulting in a new influenza virus subtype with pandemic potential. Annual vaccines are produced for routine use in protecting humans during seasonal epidemics of influenza. They offer no protection against infection with the H5N1 avian virus. For these reasons, WHO has issued guidelines for the vaccination, using the current trivalent influenza vaccine, of groups considered at high risk of exposure in countries experiencing outbreaks of highly pathogenic H5N1 avian influenza in poultry.
