How often should the seasonal influenza vaccine be administered?

The seasonal influenza vaccine should be administered annually because the virus that causes influenza changes frequently. Each year's vaccine is specifically formulated based on predictions of which strains will circulate in the upcoming flu season. This means that immunity from the previous year's vaccine may not provide sufficient protection against new strains of the virus, making an annual vaccination necessary for optimal protection.

Additionally, the immune response can wane over time, and receiving the vaccine each year helps to maintain effective immunity. Public health guidelines support annual vaccination as an essential strategy to reduce the incidence of influenza and its associated complications.