Why do we need booster doses? The primary series of vaccines kick-starts the immune response by engaging lymphocytes, white blood cells that detect specific features of the pathogen to expand in numbers and become instructed to eliminate the pathogen. Most of these cells disappear over time, except for a small subset of cells that are kept by the body for future use. These “memory cells” are responsible for long-lasting immunity against a given pathogen. What boosters do is stimulate these memory lymphocytes to quickly expand in numbers and to produce even more effective defenders. The booster also selects for B cells that can secrete antibodies that are even better at binding and blocking virus infection and spread.
The primary series can be thought of as the high school for lymphocytes, where naïve cells receive basic instructions to learn about the pathogen. Boosters are like a college where lymphocytes are further educated to become more skilled and mature, to fight off future infections. Periodically, these college graduates need refreshers by more booster doses given later in life. This is the case for all vaccines. Booster doses provide the immune system the education it needs to prevent severe diseases from infections.
COVID-19 vaccines also need booster doses for the same reasons. We need to educate, maintain, and improve T and B cell responses to prevent severe disease. Boosters provide significant benefits to people who received the primary series in preventing hospitalization and death.
Two epidemiologists explain why you'll be getting many COVID-19 boosters in the years ahead https://t.co/bh9Js9NHsA
— TIME (@TIME) July 19, 2022