It’s common for protection from vaccines to decrease over time or not be as strong against virus’ variants. A tetanus booster, for example, is recommended every 10 years and flu shots are given every year. Researchers and health officials have been monitoring the real-world performance of the COVID-19 vaccines to see how long protection lasts among vaccinated people. The vaccines authorized in the U.S. continue to offer very strong protection against severe disease and death. Tests suggest that antibodies—one of the immune system’s layers of protection—can wane over time. That does not mean the vaccine protection goes away, but it could mean that the protection is not as strong and it could take longer for the body to fight back against an infection. COVID-19 vaccine booster shots are used to provide a boost to your immune system so it can better defend against the virus.