FDA releases new data on J&J's single-dose coronavirus vaccine showing it's safe and effective

• US regulators just released detailed data on Johnson & Johnson's coronavirus vaccine.
• The single-dose vaccine will be reviewed on Friday by an expert panel that advises the FDA.
• If OK'd, J&J will ship nearly 4 million doses immediately, and plans to deliver 100 million doses by the end of June.

Johnson & Johnson's single-dose coronavirus vaccine just got one step closer to reaching the public, as US regulators released documents showing the shot was safe and confirming that it can help prevent COVID-19.

The Food and Drug Administration's 62-page review of the data found the shot to be effective and safe, and regulators said there were no identified safety issues that would prevent an emergency OK.

J&J's vaccine is widely expected to become the third COVID-19 vaccine to reach the American public. The healthcare giant has said it will have nearly 4 million doses ready to ship upon emergency authorization and is on track to deliver 100 million doses to the US by the end of June.

Like the two other US-authorized vaccines, those doses will be available at no cost to individuals in the US. The US government agreed in August to pay $1 billion to J&J for 100 million doses and the healthcare giant has pledged not to sell doses for a profit during the pandemic.

On Friday, the FDA will convene a panel of independent experts to debate and ultimately vote on whether or not to recommend J&J's jab for a regulatory OK. Experts widely expect the committee to vote in favor, and for the FDA to greenlight the shot in the following days.

J&J's vaccine was 66% effective overall, raising comparison questions with other shots

The FDA's review confirmed J&J's announcement in late-January that its vaccine was 66% effective at preventing moderate and severe cases of COVID-19.

While the efficacy easily clears the FDA's bar for authorization - set last summer at 50% - it will raise a thorny question of how the shot should be used in the real world.

The two US-authorized vaccines developed by Moderna and Pfizer were respectively 94% and 95% effective at preventing symptomatic disease. But it's difficult to directly compare the studies, as they happened at different stages in the pandemic and across different geographies.

J&J's vaccine was 72% effective in the US, 61% effective in Latin America, and 64% effective in South Africa. It's encouraging that the vaccine worked relatively well in South Africa, where a new variant is circulating.

It's unclear how well Moderna's and Pfizer's shots hold up against that variant. Those vaccines produced significantly less neutralizing antibodies, the critical virus-fighting proteins, in petri-dish testing against the variant. But it's unclear how those decreases in antibody levels translate to efficacy.

From one perspective, that makes J&J's program the only one to demonstrate the ability to protect people against the B.1.351 variant. About 19 in 20 of the infections in South Africa were caused by the B.1.351 variant. While experts anticipate the current vaccines will still be quite helpful against B.1.351, they don't yet have the clinical data to back up that hope. And AstraZeneca's vaccine program shows the risk posed by the variant, as South Africa stopped rolling out that vaccine after a study showed low efficacy against B.1.351.

J&J's shot more effective at preventing severe disease and worst COVID-19 outcomes

J&J has also emphasized its vaccine's ability to prevent the worst outcomes of COVID-19. Across the entire study's population, 31 people wound up in the hospital from COVID-19: 29 had received the placebo shot and just two had gotten J&J's vaccine. The study also tallied seven deaths - all in the placebo group.

Overall, J&J's shot was 77% effective at preventing severe disease two weeks after immunization, reaching 85% effectiveness against severe disease starting four weeks after vaccination.

While J&J said in late-January that severe disease protection was "generally consistent" across age groups, the FDA's review highlighted data suggesting the younger population may have seen stronger protection.

Starting four weeks out from immunization, the vaccine was 92% effective at preventing severe disease among adults 59 years old compared to 70% effective for those 60 years and older. However, drawing conclusions from that data may be limited by the small number of severe cases recorded among older adults.

Public-health experts are eagerly awaiting J&J's vaccine, not just to expand US supply but also for its simplicity. The one-dose jab can be stored at typical refrigerator temperatures for several months.