Pfizer has a booster shot ready to go and looking to a fourth Pfizer is ready to seek U.S. authorization for a third dose of its coronavirus vaccine, and word has it they are testing the fourth booster. Pfizer’s Dr. Mikael Dolsten told the Associated Press early data from the company’s booster study suggests people’s antibody levels rise five- to 10-fold after a third dose, compared to their second dose months earlier. In a government document referenced below, some of the very early research suggests older people who have been vaccinated are not protected from the Delta Variant.