Sister Kathe Olmstead is preparing a shot on July 27th that is part of a potential COVID-19 vaccine being 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 can not only prevent symptomatic illness, but prevent infection as well.

The company has made the additional claim to the U.S. Food and Drug Administration that would allow rival Pfizer, who could only demonstrate that its vaccine prevents symptomatic infections, including serious illnesses. It was not clear from the initial data whether the Moderna or Pfizer vaccines completely prevented infection.

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

Now Moderna says that it has also shown that its vaccine can prevent both asymptomatic and symptomatic infections.

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

Moderna found among participants who tested negative for the virus after the first smear, 14 in the vaccine group and 38 in the placebo group who tested positive for Covid-19 on the second smear. Nobody had any symptoms.

“There were approximately 2/3 fewer swabs that were positive in the vaccine group than in the placebo group at the time before dose 2, suggesting that some asymptomatic infections are prevented after the first dose,” wrote Moderna.

The company noted that this data was not included in the initial FDA approval for use in emergencies because it was not available at the time. They added it as an addendum.

The FDA’s Vaccine Advisory Board will meet on Thursday to discuss recommending the use of the Moderna vaccine, Covid-19, in people aged 18 and over.

According to the U.S. Centers for Disease Control and Prevention, around 40% of all Covid-19 cases have no symptoms.