Orthomyxoviridae - Vaccination and Prophylaxis

Vaccination and Prophylaxis

Vaccines and drugs are, however, available for the prophylaxis and treatment of influenza virus infections. Vaccines are composed of either inactivated or live attenuated virions of the H1N1 and H3N2 human influenza A viruses as well as those of influenza B viruses. Because the antigenicities of the wild viruses evolve, vaccines are reformulated annually by updating the seed strains. However, when the antigenicities of the seed strains and wild viruses do not match, vaccines fail to protect the vaccinees. In addition, even when they do match, escape mutants are often generated. The drugs include amantadine, which inhibits the uncoating of virions by interfering with M2, and oseltamivir (marketed under the brand name Tamiflu), which inhibits the release of virions from infected cells by interfering with NA. However, escape mutants are often generated for the former drug and less frequently for the latter drug.