What is a booster shot? It is an extra dose of the vaccine. In the case of the messenger RNA vaccines, it would be a third dose.
That third dose will likely be the same as the first two doses of the Pfizer-BioNTech shot. The FDA is figuring whether to give a dose of the Moderna vaccine that is lower than the first two doses given.
The extra dose mobilizes your body’s immune system defenses further to protect against Covid-19, especially variants such as Delta that are better at eluding vaccine-generated protection.
Pfizer and partner BioNTech said early testing indicates a booster shot given at least six months after the second vaccine dose produces antibody levels five to 10 times higher than after two doses.