Johnson & Johnson’s single-shot coronavirus vaccine won the backing of a panel of U.S. government advisers, paving the way for authorization of a third U.S. immunization against the deadly virus.

Experts advising the U.S. Food and Drug Administration voted 22-0, with no abstentions, that the benefits of the vaccine outweigh its risks in adults 18 and older, a decision that could help bolster the vaccine supply as new variants continue to spread. The FDA usually follows the nonbinding recommendations of its advisory panels and could authorize the shot within days.

The J&J shot is highly anticipated because it can be kept in a refrigerator for three months, an advantage over the mRNA vaccines that must be frozen when stored for longer periods, and its single-shot regime.

The vaccine was 72 per cent effective in the U.S.-based portion of a global study that enrolled more than 43,000 people, FDA staff wrote in a document released earlier this week that summarized the company’s final-stage trial results, and was 100 per cent effective in preventing death in the trial.

Quick Impact

Its effectiveness against severe disease became apparent as soon as seven days after vaccination and increased over time, company officials said at the panel meeting, rising from almost 77 per cent at least 14 days after vaccination to 85 per cent efficacy starting 28 days after vaccination. It has continued to gradually increase over time through periods longer than 56 days after vaccination, Macaya Douoguih head of medical affairs at J&J’s Janssen unit told the committee.

Overall, the rate of side effects was low. However, there were more cases of deep vein thrombosis and pulmonary embolism in people who got the vaccine compared to the placebo group, said Yosefa Hefter, a medical officer in FDA’s Center for Biologics Evaluation and Research. Also, six people who got the vaccine had ringing in their ears, compared to none in the placebo group.

A handful of serious adverse events linked to the vaccine included a case of hypersensitivity leading to lip swelling and hives, and continuing arm pain in a 30-year-old that wasn’t responsive to painkillers, Hefter said. There were also two cases of severe allergic reactions reported in a separate, independently-run study of 40,000 health-care workers in South Africa, a J&J spokesman confirmed.

Panel members agreed the one-shot vaccine works, but some wondered what will happen if a two-dose version of J&J’s vaccine in trials now proves to be more effective.

“We have a vaccine right now that has good efficacy that everyone is going to compare to the existing vaccines and say it does not look quite as good,” said Eric Rubin, a committee member who’s also editor-in-chief of the New England Journal of Medicine.

Pregnant Women

More than 30,000 women who reported themselves as pregnant have received COVID vaccines as of Feb. 16, Tom Shimabukuro of CDC’s National Center for Emerging and Zoonotic Infectious Diseases told the panel. Miscarriages reported in pregnant women who have received the vaccine haven’t occurred in numbers that raise safety concerns, he said.

J&J is planning to begin a study of the vaccine in pregnant women in March or April, Johan Van Hoof of the company’s Janssen unit, told the panel.

J&J’s vaccine differs from authorized shots from Moderna Inc. and the partnership of Pfizer Inc. and BioNTech SE, which rely on messenger RNA to turn cells into vaccine factories. It instead uses a non-replicating cold virus called an adenovirus to stimulate an immune response, preparing the body to fight COVID-19.

The company’s candidate was among six vaccines tapped for the Trump administration’s Operation Warp Speed program, receiving some US$1.5 billion in government backing. The company has a contract to deliver 100 million doses to the U.S. by the end of June.

J&J fell 2.6 per cent at the close of trading in New York.