A group of advisers to the Food and Drug Administration gave unanimous support for Johnson & Johnson’s single-shot coronavirus vaccine on Friday, setting up a decision from the agency on emergency authorization as soon as Saturday.

The committee, composed of nearly two dozen vaccine and infectious disease experts, judged the benefits of vaccination in adults older than 18 outweighed the risks in a 22-0 vote.

“It’s a relatively easy call,” said Eric Rubin, a committee member and editor-in-chief of The New England Journal of Medicine.

Despite some questions on the vaccine’s protection and use, panelists were conscious of the pressing public health threat still posed by the pandemic, even as case counts and hospitalizations have fallen sharply in the U.S.

“There’s an urgency to get this done,” said Jay Portnoy, an allergist at Children’s Mercy Hospital in Kansas City, Missouri, and a committee member. “We’re in a race between the virus mutating and new variants coming out that can cause further disease and stopping it.”

While the FDA isn’t required to follow the advice of its advisory committees, it usually does and did so twice when authorizing vaccines developed by Pfizer and Moderna last December.

“FDA staff feel the responsibility to move as quickly as possible,” wrote Janet Woodcock, the agency’s acting commissioner, on Twitter. “However, they know they must carry out their mandate to protect the public health [and] ensure any authorized vaccine meets our rigorous safety [and] effectiveness standards that the American people have come to expect.”

The FDA authorized both Pfizer’s and Moderna’s vaccines one day after their respective panel recommendations.

If cleared for use, J&J’s vaccine would represent much-needed reinforcements for an immunization campaign now well underway, although only a few million doses are expected to be immediately available.

Unlike the shots from Pfizer and Moderna, J&J’s is given as a single dose, and can be shipped at standard refrigerator temperatures. The U.S. has preordered 100 million doses, which J&J has committed to deliver by the end of June.

A large, international study of approximately 40,000 volunteers found J&J’s vaccine was 66% effective in preventing moderate or severe COVID-19. Protection was higher, at 85%, against severe disease and no participants who received the vaccine were hospitalized with COVID-19 beginning 28 days after their shot. No vaccinated volunteers died from COVID-19, either.

While efficacy was lower than what was shown by Pfizer and by Moderna in their vaccine trials, committee members appeared largely convinced an authorization of J&J’s shot was appropriate. Much of the pushback from panelists, in fact, dealt with logistic and operational details about the company’s studies, such as how it defined a COVID-19 case or how it might communicate with the public should an ongoing study show two doses to be more effective than one.

There was some discussion of the apparently lower protection offered by J&J’s vaccine against coronavirus variants first detected in South Africa and Brazil, respectively. Study results showed the shot was 64% effective against the former, known among scientists as B.1.351, and 68% effective against the latter, called P.2.

In the U.S., where neither variant was spreading when J&J tested its vaccine, efficacy was higher, at 72%.

No matter the variant, however, J&J’s vaccine was similarly strong in preventing severe COVID-19, a fact noted by FDA scientists in their review of the company’s data.

Data also appeared to show weaker efficacy in adults aged 60 and over who had underlying risk factors for worse outcomes. Both J&J and the FDA, however, argued there were too few people in the group to draw any firm conclusions — a point the panel did not dispute even when pressed by an FDA official.

Committee members did express concern that J&J’s vaccine might be perceived differently by the public than Pfizer’s or Moderna’s, and potentially affect people’s willingness to get the shot. In Europe, for example, there are reports of reluctance to get a vaccine developed by AstraZeneca and the University of Oxford because it’s viewed as less effective.

“I think it’s important that people do not think that one vaccine is better than other,” said H. Cody Meissner, a professor of pediatrics at Tufts University School of Medicine and a committee member. “Hopefully, [the Centers for Disease Control and Prevention] will emphasize that there is no preference for one vaccine over another.”

A CDC panel is scheduled to hold a meeting Sunday to discuss recommendations for use of J&J’s vaccine.

Similar to Pfizer’s and Moderna’s vaccines, J&J’s resulted in general mild or moderate reactions like injection site pain, fatigue and headache. The FDA noted more cases of hives and blood clots occurred in vaccinated volunteers than those receiving placebo, but the total number of people were very few and determined not to be caused by the vaccine.