How long does a flu vaccine protect against flu?

Many scientific studies conducted during different flu seasons have shown that a person's immunity to flu viruses (either naturally acquired or vaccinated) declines over time. The decrease of antibodies is caused by several factors - the age of the person being vaccinated and the health status of the person (e.g. chronic diseases). When healthy people get a flu vaccine, their bodies start producing antibodies and they are protected against the flu virus throughout the season. Bodies of older people and people with weakened immune systems cannot produce the same amount of antibodies after vaccination, hence they are more likely to develop mild or even severe illness, but they are protected from serious flu complications and death.

Last updated: 20-11-2023