August 4, 2021

Moderna submits data to FDA showing vaccine can potentially prevent infection, not just severe disease

Nurse Kathe Olmstead prepares a shot on July 27 that is part of a possible COVID-19 vaccine, developed by the National Institutes of Health and Moderna Inc., in Binghamton, New York. Hans Pennink/AP/File

Vaccine maker Moderna says its coronavirus shots don’t just prevent symptomatic disease, but can prevent infection in the first place.

The company has submitted to the US Food and Drug Administration with the extra claim – which would give it a leg up on rival Pfizer, which has been able to demonstrate only that its vaccine prevents symptomatic infection, including severe disease. It had not been clear from initial data if either the Moderna or Pfizer vaccines prevented infection completely.

The FDA’s own analysis of Moderna’s data confirmed the company’s claim that the vaccine was 94.5% effective at preventing severe disease 14 days after the second dose. The data submitted by Moderna looked only at cases of Covid-19 that exhibited symptoms and found that the vaccine was effective at reducing cases of Covid-19 with severe symptoms.

Now Moderna says it has also shown its vaccine can prevent asymptomatic as well as symptomatic infection.

To determine if the vaccine reduced the rate of overall infection, the researchers took nasal swabs of volunteers before each shot and tested them for Covid-19. Moderna’s vaccine requires a two shots given four weeks apart.

Moderna found among those participants who tested negative for the virus after the first swab, 14 in the vaccine group and 38 in the placebo group tested positive for Covid-19 when swabbed the second time. None had any symptoms.

“There were approximately 2/3 fewer swabs that were positive in the vaccine group as compared to the placebo group at the pre-dose 2 timepoint, suggesting that some asymptomatic infections start to be prevented after the first dose,” Moderna wrote.

The company noted that they did not include this data in the initial emergency use authorization submission to the FDA because it was unavailable at the time. They included it as an addendum. 

The FDA’s vaccine advisory committee will be meeting on Thursday to discuss recommending the use of Moderna’s Covid-19 vaccine in people 18 years and older.

According to the US Centers for Disease Control and Prevention, about 40% of all Covid-19 cases exhibit no symptoms.