Flexi Says: A booster shot is an extra administration of a vaccine after the first vaccination. The booster re-exposes the immune system to the immunizing antigen after memory cells against that antigen have declined over time. When the booster is received, the immune system generates more antibodies to increase protection from the disease. For example, tetanus shot boosters are often recommended every 10 years, before which memory cells specific against tetanus have lost their function or have undergone apoptosis. Another example is the booster shot for the COVID-19 vaccine. A booster shot is typically similar to the initial dose.
