Despite the 95 percent effectiveness at preventing coronavirus infection after two doses of its vaccine, Pfizer is now seeing what a third dose might do.
The company announced Thursday that a booster dose is being studied among people who received their first doses of the vaccine more than six months ago. In an interview with NBC News' Lester Holt, Pfizer CEO Albert Bourla said the hope is that a third dose will boost the immune response even higher, offering better protection against variants.
"We believe that the third dose," Bourla said, "will raise the antibody response 10- to 20- fold."
The new study will monitor the safety and efficacy of a third dose in two age groups: those 18 to 55 and those 65 to 85. The participants come from a group of people who were among the first to receive the Pfizer-BioNTech vaccine: people who volunteered for Pfizer's initial Phase 1/2 clinical trial, which began in May.