FDA advisory panel recommends Johnson & Johnson COVID-19 vaccine be cleared for use. Authorization is likely this weekend

Emergency use approval from the agency is likely to follow.

The Johnson & Johnson vaccine requires just one dose and can be stored in standard refrigerators.Associated Press

An influential panel of medical experts on Friday unanimously recommended that drug regulators clear Johnson & Johnson’s COVID-19 vaccine for emergency use, setting the stage for the likely authorization of the third such vaccine in the United States — and the first that would require just one shot.

Only days after the nation passed the grim milestone of 500,000 coronavirus-related deaths, the advisory committee to the Food and Drug Administration agreed on a 22-0 vote that the benefits of the vaccine outweigh its risks for people 18 and older.

The FDA is widely expected to act favorably on the recommendation this weekend. Johnson & Johnson said that once authorization is granted, it would start shipping 4 million doses within days, 20 million by the end of March, and 100 million by the end of June. The infusion would ease the shortage of vaccines and, potentially, help tame the pandemic.

The advisory panel was particularly encouraged that the vaccine, which the pharmaceutical giant tested on about 44,000 volunteers globally, provided robust protection against severe disease caused by resistant virus variants that are widespread in the United Kingdom, South Africa, and Brazil. Those variants emerged after large studies of the first two authorized vaccines, from Pfizer-BioNTech and Cambridge-based Moderna, were conducted last year. The newer strains appear to be more contagious and potentially more dangerous, and have caused a rising number of confirmed case in the United States.

“We’re in a race,” said Dr. Jay Portnoy, a pediatrician at Children’s Mercy Hospital in Kansas City, Mo., and a committee member. The longer the pandemic lasts, he noted, the more likely other worrisome variants will emerge. “We need to get this vaccine out,” he added.

Johnson & Johnson developed the vaccine with Beth Israel Deaconess Medical Center, whose Center for Virology and Vaccine Research licensed technology to the New Brunswick, N.J., company.

Dr. Dan Barouch, head of Beth Israel’s virology center, said he followed the committee meeting, which was streamed online, and was thrilled with the vote. He said he had no doubt that the vaccine will save lives and planned to celebrate with his wife and two daughters over a takeout meal and Champagne.

“I couldn’t be happier,” Barouch said in a phone interview.

Acting FDA Commissioner Janet Woodcock and Dr. Peter Marks, director of the agency’s Center for Biologics Evaluations and Research, said in a statement Friday evening that the FDA will work swiftly “toward finalization and issuance of an emergency use authorization.”

Overall, the Johnson & Johnson vaccine was 72 percent effective at preventing moderate to severe disease in the United States and 66 percent effective globally, according to the latest data. In trial sites across all regions, it was 85 percent effective at preventing severe illness and 100 percent effective at preventing coronavirus-related hospitalization and death.

Those figures generally fell short of the stellar performances of two-dose vaccines from Pfizer-BioNTech and Moderna that were cleared for use in December. Those vaccines prevented about 95 percent of coronavirus cases in large studies. But the trials were held before resistant variants emerged, and federal health officials and vaccine experts say the percentages would undoubtedly be lower if those studies were conducted now.

Indeed, the variants blunted the effectiveness of the Johnson & Johnson vaccine in trial sites in Brazil and South Africa. The vaccine was 68 percent effective at preventing moderate to severe disease caused by the dominant variant in Brazil and 64 percent effective against the dominant variant in South Africa.

Still, those figures exceeded the efficacy rate of 50 percent that Dr. Anthony Fauci, the nation’s top infectious disease expert, said last summer that a COVID-19 vaccine would have to reach for the government to authorize it for use. By comparison, the seasonal flu shot is typically 40 to 60 percent effective, according to the CDC.

Johnson & Johnson executives and FDA experts said Friday that the vaccine is safe and generally caused only mild side effects.

With the FDA poised to clear a third vaccine, several committee members took pains to discourage the public from shopping around for the one they think will be most effective.

“It’s important that people do not think that one vaccine is better than another,” said Dr. H. Cody Meissner, a professor of pediatrics at the Tufts University School of Medicine.

“Whatever you can get, get,” agreed Dr. Arnold Monto, a professor of epidemiology at the University of Michigan School of Public Health and acting chair of the advisory panel, which is officially called the Vaccines and Related Biological Products Advisory Committee.

Many Americans would welcome a third vaccine, given the frustratingly slow and uneven rollout of the first two.

Some 70.5 million doses of the Pfizer-BioNTech and Moderna vaccines had been administered as of Friday, according to the US Centers for Disease Control and Prevention. The Johnson & Johnson vaccine would go twice as far as its rivals because it requires only one dose.

The Johnson & Johnson vaccine has another key advantage. It can be stored in standard refrigerators, unlike the vaccines from Pfizer-BioNTech and Moderna, which must be shipped and stored frozen.

Several committee members noted that Johnson & Johnson has a late-stage trial testing two doses of the vaccine on 30,000 volunteers. They expressed concern that if the FDA grants emergency use, the company may need to come back in a few months and ask for the authorization to be revised if two doses turns out to be more effective than one.

That wouldn’t be a problem, Barouch told the Globe. He noted that Pfizer-BioNTech and Moderna are both testing potential booster shots to address variants.

“If a two-shot version of the [Johnson & Johnson] vaccine is even better, then people could be boosted if they want to,” he said.

Like Moderna, the Johnson & Johnson vaccine was heavily bankrolled by US taxpayers. The federal government and Johnson & Johnson invested more than $1 billion in the vaccine as part of a deal signed last March that secured 100 million vaccine doses and an option for 200 million more.

As with the messenger RNA vaccines made by Pfizer-BioNTech and Moderna, Johnson & Johnson’s vaccine relies on a cutting-edge approach to stimulating immunity. It uses a harmless and relatively rare cold virus, adenovirus serotype 26 — or Ad26 — as a Trojan horse to deliver part of the distinctive spike protein on the coronavirus surface into cells to trigger an immune response without making people sick. Adenovirus-based vaccines have been investigated for about three decades but have yet to be licensed for use in the United States.