Pfizer said Oct. 21 people who received a 30 microgram booster dose of its COVID-19 vaccine saw higher immunity levels than those who did not receive a booster.
The drugmaker conducted a phase 3 trial involving more than 10,000 participants ages 16 and older who received two doses of Pfizer's COVID-19 vaccine. Half of the participants received a booster dose and half received a placebo. The median time between the second dose and the administration of the booster or placebo was about 11 months.
Participants who received a booster dose restored their immunity to the same high levels achieved after their second dose, as the research team observed the vaccine's efficacy to be 95.6 percent among this group.
Pfizer said the results were the first to come from a randomized, controlled COVID-19 vaccine booster trial.