Influenza viruses circulate predominantly in the winter months in temperate regions (typically November–April in the Northern Hemisphere and April–September in the Southern Hemisphere) but can occur year-round in tropical climates. Annual influenza vaccination of all people aged ≥6 months is recommended as the most effective measure for preventing influenza and its associated complications. Prevention of influenza is particularly important for people who are (or live with those who are) at increased risk for influenza-related complications, such as children aged <5 years (particularly infants aged <6 months who are not eligible for influenza vaccination), people with medical conditions (such as immunosuppression, diabetes, asthma, pregnancy, and neurologic disorders) and children and adolescents who are receiving long-term aspirin therapy.
Vaccination is the best protection against the flu and its complications. This vaccine does not protect against colds and respiratory infections caused by other viruses.