WASHINGTON: The single-shot Johnson & Johnson vaccine is highly effective in preventing severe Covid-19, including newer variants, according to documents released by the US Food and Drug Administration on Wednesday.

The news came as the regulator was set to convene an independent panel Friday that will likely vote to authorize the vaccine, making it the third available in the country hit hardest by the coronavirus pandemic.

In large clinical trials, the J&J vaccine’s efficacy against severe disease was 85.9 percent in the United States, 81.7 percent in South Africa, and 87.6 percent in Brazil.

Overall, among 39,321 participants across all regions, the efficacy against severe Covid-19 was 85.4 percent, but it fell to 66.1 percent when including moderate forms of the disease.

Crucially, analyses of different demographic groups revealed no marked differences across age, race, or people with underlying conditions.

The vaccine was generally well-tolerated, with no reports of severe allergic reactions (anaphylaxis), which have been seen in rare cases for the Pfizer and Moderna shots. Mild to moderate reactions, like injection-site pain, headache, fatigue and muscle pains were more likely to occur in younger participants than older. There were no reported deaths in the vaccine group, but five in the placebo group.