Johnson & Johnson's single-dose COVID-19 vaccine effective, safe: FDA analysis

Johnson & Johnson's single-dose coronavirus vaccine is effective at preventing moderate and severe cases of COVID-19, according to an analysis of the trial data published by the Food and Drug Administration on Wednesday.

The company's single dose vaccine is 66 percent effective, well within the agency's standards. The vaccine is also safe to use, according to the analysis.

More specifically, the vaccine is more than 85 percent effective at preventing severe cases of COVID-19 and completely prevents hospitalizations and deaths.

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Overall, there were seven deaths in the trial, all in the placebo group.

The company initially announced the 66 percent effectiveness in a press release last month but had not yet released trial results.

The information was published ahead of an FDA advisory committee meeting Friday, which will debate whether to grant the vaccine emergency authorization. The promising data gives hope that a third coronavirus vaccine could be authorized as soon as this weekend.

While the other coronavirus vaccines already on the market may appear to be more effective than Johnson & Johnson's, experts say it is difficult to compare them head-to-head.

The vaccine was tested in a 44,000-person clinical trial across the U.S., Brazil and South Africa geographic regions, all of which have seen mutated versions of the virus. 

There was a lower efficacy against moderate to severe/critical disease endpoints observed in South Africa compared to the United States and Brazil, but vaccine efficacy against severe or critical COVID-19 infections was "similarly high in all 3 countries," the review found.

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Still, the varying efficacy is a warning sign about mutations, especially from the variant found in South Africa. The effectiveness against moderate to severe illness dropped from 72 percent in the United States to 57 percent in South Africa, where a new coronavirus variant is prevalent.

The vaccine was less effective in a subgroup of adults older than 60 with underlying conditions, but regulators noted there were no deaths or cases requiring medical intervention a month after those older adults received vaccines.

The most frequently reported local adverse reaction was injection site pain, which was reported more by younger participants aged 18 to 59 than people older than 60.

If granted authorization, the U.S. won't see a significant increase in available vaccine supply. Johnson & Johnson has said it will have about 4 million doses ready to ship immediately upon emergency authorization. A company executive told Congress that it expects to provide 20 million doses by the end of March and 100 million by summer.

However, the shot could ease the complicated logistics of the U.S. vaccine rollout. Unlike the vaccines from Moderna and Pfizer, Johnson & Johnson's shot can be stored in a normal refrigerator for several months, rather than at ultra-cold temperatures.

And as a single shot, there won't be a concern about scheduling or having enough supplies for a second dose.

Updated at 9:38 a.m.