Does the Flu Vaccine Take Effect Immediately on the Day of Injection?

Question

Does the flu vaccine work immediately on the day of injection? Isn’t each flu season different? What should I do to prevent it?

Answer

The flu vaccine does not take effect immediately on the day of injection. It usually takes about two weeks for the body to develop sufficient immunity to the vaccine. During this time, recipients may still be infected with the flu. However, once the vaccine becomes fully effective, it will help the body build resistance to specific flu virus strains and provide protection throughout the upcoming flu season. Although flu virus strains change over time, each year’s flu vaccine is formulated based on the current expected most prevalent strains, making vaccination still the most effective preventive measure. Additionally, maintaining good personal hygiene habits, such as frequent handwashing and avoiding touching your eyes, nose, and mouth, also helps reduce the risk of getting the flu.