The protection provided by a flu shot typically lasts for about six months. The flu vaccine is designed to protect against the most common strains of the influenza virus for each flu season. For most people, the flu shot offers the highest level of protection within the first two to three months after vaccination, but the immunity gradually diminishes over time. For this reason, annual flu shots are recommended, especially for those who are most at risk, such as older adults, children, pregnant women, and individuals with compromised immune systems.

The flu virus can also change from year to year due to its ability to undergo antigenic drift, which is a process where small changes in the virus’s surface proteins make it harder for the immune system to recognize and fight the virus. That’s why it’s essential to get the flu shot every year, as each year’s vaccine is formulated to protect against the most current strains of the virus. Even if you are vaccinated, it is still possible to catch a flu strain that wasn't included in the vaccine, but the flu shot may reduce the severity of illness or the risk of complications. For optimal protection, it is recommended to get the flu shot in the early fall before the flu season peaks.

Vaccinations and immunizations play a crucial role in preventing the spread of infectious diseases by preparing the body’s immune system to recognize and fight specific pathogens. When a person receives a vaccination, a weakened or inactive form of a virus or bacteria-or a piece of it-is introduced into the body. This triggers the immune system to produce antibodies without causing the actual illness. These antibodies remain in the system, ready to respond quickly if the person is later exposed to the real infection, significantly reducing the risk of developing severe symptoms or complications.

At the community level, widespread vaccination creates what is known as herd immunity. This means that when enough people are protected against a disease, its spread slows or stops, indirectly safeguarding those who cannot be vaccinated, such as newborns or individuals with weakened immune systems. This collective protection has been instrumental in eradicating or controlling diseases like smallpox, polio, and measles, showcasing the lasting benefits of immunization programs worldwide.