[Read more about Moderna's Covid-19 vaccine.]
Pfizer gave fewer details in its announcement last week on November 9th than Moderna on Monday, November 16. Pfizer's external panel of experts analyzed 94 volunteers and estimated the effectiveness of its vaccine to be over 90 percent. They didn't say how many people who got sick received the vaccine or the placebo.
Even so, the estimates for the two vaccines are clearly in the same range. In addition, both of them far exceed the F.D.A.'s requirement that coronavirus vaccines be greater than 50 percent effectiveness.
Pfizer did not report how many volunteers had severe Covid-19 or what proportion of those people received the vaccine. Results like these are expected to be published in the next few weeks.