The Food and Drug Administration has authorized Johnson & Johnson’s one-dose COVID-19 vaccine for emergency use during the pandemic, its third EUA for a vaccine against the disease.

The drug, green-lit by independent advisors, is approved for use in adults aged 18 years and older. It was vetted using data from an ongoing study of more than 43,000 participants in the U.S., South Africa, South America and Mexico. 

That data show that the vaccine was approximately 67% effective overall in preventing moderate to severe/critical COVID-19 at least 14 days after vaccination, the agency reported. That’s lower than the Pfizer and Moderna vaccines, which each have overall efficacy of 94% or higher. 

But if an inoculated person does contract the disease, J&J’s drug is “virtually 100% effective” at protecting against hospitalization, ICU admission and death, Paul Offit, M.D., a member of the FDA’s advisory panel, told NPR on Weekend Edition Saturday. “This certainly provides protection against what you care about,” he said.

Participants in the J&J trials were followed for a median of eight weeks, and most side effects were typical of vaccination, mild to moderate, and short-lasting.

“The authorization of this vaccine expands the availability of vaccines, the best medical prevention method for COVID-19, to help us in the fight against this pandemic, which has claimed over half a million lives in the United States,” said Acting FDA Commissioner Janet Woodcock, M.D., in a statement.