What we know about whether we’ll need booster vaccines

How long is a person immune after having Covid-19, after getting vaccinated, or both? And what could long-lasting immunity mean for booster shots?    Immunity is often measured by antibodies -- proteins made by the immune system to help fight infections in the blood. That can usually be determined with a laboratory test. But immune systems include much more than just antibodies; they involve a host of players including B cells, which produce antibodies, and T cells, which target infected cells.   Research has shown that both antibodies and T cells might even recognize infections from variants of a pathogen -- such as the emerging coronavirus variants circulating in the world today, which, despite key differences that may make them spread more easily, have enough similarities to be recognized by the immune system's memory.   Even if someone recovered from a previous infection and has a natural immunity, vaccinations can help give their immune memory a boost.   "More research must be done to understand what type and level of antibodies suggest protection from reinfection," Dr. Brian Caveney, chief medical officer and president of Labcorp Diagnostics, said in a news release last week. "But the prolonged presence of certain antibodies is a promising sign as we continue thinking about safely emerging from the pandemic, as well as future vaccinations and the timing of booster shots."