Moderna's vaccine is safe and effective for preventing Covid-19, US regulators said, clearing the way for a second shot to quickly gain emergency authorization and add to the country's sprawling immunization effort.
The Food and Drug Administration's staff said in a report on Tuesday that the experimental vaccine is 94.1% effective at preventing symptomatic Covid-19, confirming earlier results released by the company.
The report was posted online ahead of a meeting on Thursday of agency advisers, who will vote on whether to recommend authorization before a final FDA decision.
The agency does not have to follow the advice of the independent vaccine experts, though it often agrees with its advisory panels. Last week, the FDA authorized a similar vaccine from Pfizer and BioNTech after an advisory panel voted 17-4, with one abstention, to support its authorization.
The FDA got a much deeper look at Moderna's clinical-trial data than the numbers previously released to the public by the company.
Notably, the agency was able to review the shot's effectiveness across a broad range of racial, ethnic and age groups, and look at evidence of how well the shot worked for people with pre-existing medical conditions that make them more vulnerable to severe Covid-19.
The agency found the shot was similarly effective across racial and ethnic groups and those with underlying medical conditions. It was 86.4% effective in people age 65 and over, according to the report, and 95.6% effective in those 18 to 65.
Both the Moderna vaccine and the Pfizer vaccine are based on messenger RNA technology that has not been previously used in inoculations. Additionally, both are two-dose vaccines, meaning once people receive an initial shot, they will need to return to their care providers weeks later for an additional injection.
Between Pfizer and Moderna, Operation Warp Speed officials have said 20 million people in the United States are expected to get their first shots by year-end.
Moderna's vaccine is not yet approved in any other countries and has not yet been used on anyone outside of a clinical trial.
Once the US grants authorization, advisers to the Centers for Disease Control and Prevention must meet, as they did last week on Pfizer's vaccine, to give Moderna's shot the green light and provide offer specific recommendations for use and monitoring.