Antibodies to SARS-CoV-2, the virus that causes COVID-19, can be detected in the blood of people who have recovered from COVID-19 or people who have been vaccinated against COVID-19. Getting a vaccine is safer than getting COVID-19, and vaccination against COVID-19 is recommended for everyone 5 years of age and older. If someone has already had COVID-19, vaccination against COVID-19 increases their body’s antibody response, which improves their protection.

It is important to remember that some people with antibodies to SARS-CoV-2 may become infected after vaccination (vaccine breakthrough infection) or after recovering from a past infection (reinfected). Based on what we know right now, risk of reinfection is low for at least the first 6 months following an infection with the virus that causes COVID-19 diagnosed by a laboratory test. When someone who is fully vaccinated gets COVID-19, it is called a vaccine breakthrough infection. No vaccine is 100% effective, so some breakthrough infections are expected. The risk of infection, severe illness, hospitalization, and death are all much lower for vaccinated people compared to people who are unvaccinated. When reinfections or breakthrough infections happen, having antibodies plays an important role in helping prevent severe illness, hospitalization, and death.

For many diseases, including COVID-19, antibodies are expected to decrease or “wane” over time. After a long enough period of time, your level of antibodies can decrease below a level that provides effective protection. This level is called the “threshold of protection.” When antibodies decrease below the threshold of protection, you may become more vulnerable to severe illness. We do not yet know what the threshold of protection for antibodies is for the virus that causes COVID-19 or how long it takes these antibodies to wane. Even after antibodies wane, your immune system may have cells that remember the virus that can act quickly to protect you from severe illness if you become infected. These topics are being researched by scientists all over the world.