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Moderna says vaccine prevents COVID-19 in large study, adding to hopes for several protective shots

An experimental vaccine developed by Moderna and U.S. government scientists protected participants in a large U.S. study from developing COVID-19, a significant and anticipated finding that makes it more likely multiple coronavirus shots may soon be available to help slow the surging pandemic.

The result, which Moderna announced Monday morning, is from an early look at a clinical trial of 30,000 volunteers recruited at nearly 90 hospitals and clinics across the country. An independent committee overseeing the trial found Moderna’s vaccine was 94.5% effective at preventing COVID-19 compared to a placebo. Their analysis was based on 95 cases of COVID-19, 90 of which occurred in participants given the placebo versus just five among those who received the vaccine.

Crucially, while 11 participants given the placebo developed severe COVID-19, there were no such cases in vaccinated individuals, suggesting inoculation protects against the worst symptoms of the disease.

So far, side effects to vaccination have mostly been mild to moderate in nature, Moderna said. More severe reactions were observed in smaller proportions of participants, most commonly fatigue, pain, headache and injection site redness after the second vaccine dose. The trial monitoring committee, which reviewed available data, reported no significant safety concerns.

The company plans to seek emergency clearance in the U.S. “in the coming weeks,” according to a statement, and will follow up with applications to regulators overseas as well.

Guidelines issued by the Food and Drug Administration require a median of at least two months’ worth of safety follow-up for any emergency approval of a coronavirus vaccine — a bar Moderna expects it will meet shortly.

Moderna’s success comes just a week after partners Pfizer and BioNTech said their shot was more than 90% effective at preventing COVID-19, an estimate based on 94 reported cases in the companies’ own large trial. Pfizer and BioNTech’s finding had heightened expectations that Moderna’s vaccine, which is based on the same technology, would be similarly effective.

The results are “mutually reinforcing,” said Tal Zaks, Moderna’s chief medical officer, in an interview. “I think there’s a strong sense of scientific affirmation.”

Moderna’s announcement, while another major milestone in researchers’ race to develop a vaccine, didn’t include important details that will only come with time. It’s unclear, for instance, how long the vaccine’s protective benefit might last, or whether vaccination protects against infection as well as disease. The estimate for the vaccine’s effectiveness may also change as more participants develop COVID-19 in the trial, which will continue through to a final analysis when 151 cases have occurred.

Still, the trial’s positive outcome is a resounding achievement at a time when the world needs one, with infections and hospitalizations accelerating in the U.S. and abroad. More than one million Americans tested positive in the seven days from Nov. 8 to Nov. 15, according to data collected by The New York Times.

The results are also a promise kept at the most critical moment for Moderna, after the company spent years touting the world-changing potential of its technology, and after a record-breaking push over 10 months to design, develop and test a vaccine against the new coronavirus.

Moderna was the first coronavirus vaccine developer to reach a number of significant development milestones. The biotech had recently slowed enrollment into its late-stage study, however, in an effort to recruit a more diverse group of participants.

Moderna said Monday that 15 of the COVID-19 cases involved in its interim analysis occurred in people over 65 years of age, while 20 were in people who identify as Black, Hispanic or Latino, Asian American or multiracial.​ Testing in a range of different groups is important to proving a vaccine can work for everyone, especially communities most at risk from COVID-19.

In meeting the high bar set by BioNTech and Pfizer, Moderna’s finding boosts the prospects of an effective vaccine eventually being widely available, since at least several will likely be needed to cover the world’s population. All vaccines in human testing, in one way or another, target a spiky protein on the coronavirus surface, making the success of two a strong signal others could follow suit.

“[This] absolutely demonstrates that focusing on the spike protein is the right thing to do,” said Moderna’s Zaks.

Neither Pfizer nor Moderna have disclosed detailed data, likely because they don’t yet have that information in hand. In both cases, the company’s announcements followed meetings of data monitoring boards that review trial data independently of the companies. But those specifics will be critical to more fully assess each vaccine’s effectiveness and potential utility.

The FDA has said it will convene a panel of expert advisers to publicly review every application for a coronavirus vaccine emergency approval.

Should the FDA clear Moderna’s as well as Pfizer and BioNTech’s vaccines, supplies this year will be limited to about 50 to 60 million doses in the U.S. — 20 million from Moderna and 30 to 40 million from Pfizer and BioNTech. Each vaccine is given over two shots.