Pfizer provided less detail in its announcement last week on Nov. 9 than Moderna did on Monday, Nov. 16. Pfizer’s outside board of experts analyzed 94 volunteers and estimated that the effectiveness of its vaccine was over 90 percent. They did not specify how many people who got sick had received the vaccine or the placebo.
Nevertheless, the estimates for the two vaccines are clearly in the same ballpark. What’s more, they both far exceed the F.D.A.’s requirement that coronavirus vaccines have an efficacy of more than 50 percent.
Pfizer did not report how many volunteers had severe Covid-19, or what fraction of those people got the vaccine. Findings like these are expected to come out in the next few weeks.