The Food and Drug Administration's staff released a briefing document on Wednesday endorsing Johnson & Johnson's one-shot coronavirus vaccine as safe and effective.

What's next: An FDA advisory panel will meet Friday to review the briefing document and vote on whether to recommend an emergency use authorization (EUA). The FDA could then issue the (EUA) as soon as this weekend, clearing the way for distribution in the U.S. to begin.

Details: The shot was found to be 66.9% effective against moderate to severe COVID-19 14 days after vaccination, and 66.1% effective after 28 days. "The analysis supported a favorable safety profile with no specific safety concerns identified that would preclude issuance of an EUA," FDA staff wrote.

Between the lines: Unlike Moderna and Pfizer's vaccines, which are the only two candidates that have received EUAs, the J&J vaccine is administered as a single dose and does not need to be stored at ultra-low temperatures.

The big picture: The U.S. government has struck an agreement with J&J to provide 100 million doses by the end of June, but White House coronavirus coordinator Jeff Zients has cautioned that the company likely will not have a “big inventory” of doses immediately ready for distribution.

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