The single-shot vaccine is highly effective in preventing severe Covid-19, including against newer variants, the Food and Drug Administration (FDA) said before giving it a greenlight.
“The authorization of this vaccine expands the availability of vaccines, the best medical prevention method for Covid-19, to help us in the fight against this pandemic, which has claimed over half a million lives in the United States,” said the US regulator’s acting director Janet Woodcock.
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 various demographic groups revealed no marked differences across age, race, or people with underlying conditions.
A third vaccine is seen as a vital means to ramp up the immunization rate in the United States, where more than 500,000 people have lost their lives to the coronavirus.
The J&J vaccine is the third to be greenlighted in the United States after Pfizer’s and Moderna’s were provisionally approved in December.
Over 65 million people in America have so far received at least one shot of either the Pfizer or Moderna vaccines — but unlike those, the J&J vaccine requires just one dose, and is stored at fridge temperatures, offering logistical and practical advantages.
The J&J shot is slightly less protective than Pfizer and Moderna’s two-shot regimens, which both have an efficacy of around 95 percent against all forms of Covid-19 from the classic coronavirus strain.
There was a hint, based on preliminary data, that the vaccine might be effective against asymptomatic infection — though J&J said it needs to do more research to confirm this.
The company has announced it aims to deliver a total of 20 million doses by the end of March, with 100 million by June — though the US is pushing to expedite that timeline.
The J&J vaccine uses a common-cold causing adenovirus, which has been genetically modified so that it can’t replicate, to carry the gene for a key protein of the coronavirus into human cells.