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U.S.-supported COVID-19 vaccine candidates appear highly effective
November 19, 2020

Moderna scientist working in a lab.
Moderna scientists working in partnership with the U.S. government have developed a vaccine candidate found to be nearly 95% effective in preventing COVID-19. (© David L. Ryan/The Boston Globe/Getty Images)


Two U.S.-supported COVID-19 vaccine candidates appear to be highly effective at preventing COVID-19, a major step in the United States’ historic push to end the global pandemic.

Moderna announced November 16 that the Phase 3 clinical trial’s independent data and safety monitoring board had found the Massachusetts-based biotechnology company’s candidate vaccine is up to 94.5% effective in clinical trials.

Pfizer, based in New York, announced November 18 that its candidate vaccine appears to be 95% effective in preventing COVID-19 at 28 days after the first dose.

“Since early January, we have chased this virus with the intent to protect as many people around the world as possible,” Moderna’s Chief Executive Officer Stéphane Bancel said in a statement. “I want to thank our partners at BARDA [the U.S. Biomedical Advanced Research and Development Authority] and Operation Warp Speed, who have been instrumental to accelerating our progress to this point.”

Moderna developed its vaccine in partnership with the U.S. National Institutes of Health (NIH), while Pfizer developed its vaccine in partnership with the German company BioNTech. The U.S. government has committed to purchasing doses of both candidate vaccines.

While vaccine development and testing normally takes years, the Trump administration is investing billions of dollars to accelerate the development, clinical trials, manufacture and distribution of vaccines through Operation Warp Speed.

As part of this effort, the United States is convening government scientists, private pharmaceutical companies and university researchers with the goal of finding a safe and effective vaccine before the end of the year.

The United States has also supported four other candidate vaccines, including a candidate that AstraZeneca, headquartered in the United Kingdom, advanced to Phase 3 of clinical testing in August.

In the Phase 3 trials, researchers split participants into two groups and gave one group the vaccine and the other a placebo. In the Moderna trial, interim analysis found that of 95 study participants who contracted COVID-19, 90 were part of the placebo group while only five participants who had received the vaccine developed COVID-19, NIH said in a statement.

In the Pfizer trial, researchers found that of 170 participants who contracted COVID-19, 162 received the placebo while only eight had received the vaccine. Of the 10 people who developed severe COVID-19 in Pfizer’s trial, only one had received the vaccine. The company announced the completion of the Phase 3 trials on November 18.

Dr. Anthony Fauci, the director of NIH’s National Institute of Allergy and Infectious Diseases, told NBC on November 16 that Moderna’s vaccine could be distributed to at-risk populations as soon as December. But U.S. officials will not compromise safety in determining when to release the vaccine, he said.

“It’s going to be all hands on deck” to produce and distribute the vaccines, Fauci told the news network. “They’re not going to cut any corners, but they’re going to do it quickly.”