Based on the encouraging findings, the agency intends to grant emergency authorization for use of the vaccine Friday, people familiar with the FDA’s plans said. The decision would give millions of Americans access to a second coronavirus vaccine beginning as early as next week.
The review by the FDA confirms Moderna’s earlier assessment that its vaccine had an efficacy rate of 94.1% in a trial of 30,000 people. Side effects, including fever, headache and fatigue, were unpleasant but not dangerous, the agency found.
The success of Moderna’s vaccine has become all the more crucial to fighting the pandemic as other vaccine efforts have faltered. The hopeful news arrives at a time of record-breaking numbers of coronavirus cases that are overwhelming hospitals and of an ever-increasing death toll, which reached a bleak milestone of 300,000 on Monday.
The data release is the first step of a public review process that will include a daylong meeting Thursday by an independent advisory panel of experts. They will hear from Moderna, FDA scientists and the public before voting on whether to recommend authorization. The panel is expected to vote yes, and the FDA generally follows the experts’ recommendations.
Distribution of about 6 million doses could then begin next week, significantly adding to the millions of doses already being shipped by Pfizer and BioNTech, the companies that developed the first coronavirus vaccine given emergency clearance Friday. Health care workers received the first shots Monday of the Pfizer-BioNTech vaccine, which has an efficacy rate of 95%.
The vaccine rollout has been highly anticipated and is one of the most ambitious immunization campaigns ever conducted in the United States.
The federal government signed deals last summer with Moderna and Pfizer to deliver a total of 200 million doses in the first quarter of 2021. Because both vaccines require two doses, those contracts guaranteed enough doses for 100 million people.
Last week the government announced that it had purchased another 100 million doses from Moderna for the second quarter, increasing the number of Americans who can be vaccinated to 150 million. But that still leaves the question of how and when the roughly 180 million other Americans will be covered.
Both vaccines will be provided to the public free of charge.
Moderna’s vaccine worked equally well in white volunteers and in communities of color. There was also no significant difference between its protection for men and women, or between healthy volunteers and those at risk of severe COVID-19 who had conditions like obesity and diabetes. For people 65 and older, the trial provided an estimated efficacy of 86.4%, lower than the overall estimate of 94.1%. But the apparent difference was not statistically significant.
So far, two potential differences between the vaccines have emerged from the FDA’s reviews, but the findings may reflect a shortage of data rather than genuine differences. The Pfizer-BioNTech trial showed that their vaccine started to protect against the coronavirus within about 10 days of the first dose. The trial of Moderna’s vaccine, by contrast, did not reveal such a striking effect after the first dose.
But fewer cases of COVID-19 occurred among trial participants in the early days of the Moderna trial, making it harder to measure differences between the vaccinated group and the placebo group. In any case, health officials have said that for both vaccines, two doses are essential for full protection.
A second difference involves the ability to prevent severe disease. Moderna produced more evidence that its vaccine can do so, according to the review. In its trial, 30 volunteers developed severe cases of COVID. All of them were in the placebo group, with no cases among the people who were vaccinated.
In the Pfizer-BioNTech trial, the findings were less compelling. There were 10 severe cases in the placebo group and one in the vaccinated group. Those numbers are too small to gauge the vaccine’s ability to prevent serious illness.
“The available data for these outcomes did not allow for firm conclusions,” the FDA said.
The documents published Tuesday made clear that side effects were particularly common after the second dose but typically lasted only a day. Experts say people may need to take a day off work after getting the shot.