What Happens To Your Body When You Get A Booster Shot

In an ideal world, one round of vaccine shots would be all that is necessary to protect against a disease, and oftentimes, that is actually the case. However, some diseases require that you come in for another round of shots after a certain amount of time has passed. This is the case for tetanus, which necessitates a booster shot every decade (per CDC).

In addition, there has been recent discussion about whether booster shots may be necessary for COVID-19 vaccine recipients. Recent research suggests this may not be the case for Moderna and Pfizer vaccines (per New York Times). However, for Johnson & Johnson vaccine recipients, the need for a booster shot may be more likely (per Reuters). Regardless, the research is still being conducted for each of these vaccines, according to Dr. Anthony Fauci (via PBS).

With this in mind, you may be wondering what a booster shot actually does, and how it helps protect you against diseases.

It is currently unknown why some diseases require booster shots and others do not. According to History of Vaccines, a resource by The College of Physicians of Philadelphia, some research suggests that the distinction may have to do with how rapidly the disease generally progresses through the body. If the progression is typically very fast, then it may outpace the immune system. Booster shots serve as a reminder to the immune system to keep looking out for the disease so that it can recognize it quickly and nip it in the bud regardless of its speed.

There are a couple factors that go into deciding whether a booster shot is necessary for a specific vaccine. The primary factor is the durability of the protection; as more research is collected over time, do breakthrough infections remain low, or do they start to exceed the expected threshold? If the latter is the case, a booster may need to be developed to better train people's immune systems to continue fighting against the disease in question. In the case of COVID-19, Dr. Anthony Fauci reported that booster shots may be necessary if variants start to circumvent our current vaccines, but fortunately, this does not yet seem to be a problem (via PBS).