Influenza and influenza vaccination.

The hemagglutinin and neuraminidase surface antigens of the influenza virus periodically undergo major or minor structural changes. These influence epidemiologic patterns and the composition of vaccine. Annual vaccination is recommended for individuals at increased risk of complications from lower respiratory tract infections. Vaccine for 1979-80 contains antigens representative of three viruses and is closely related to the vaccine of 1978-79. Amantadine is approved for prophylaxis and treatment.