Johnson & Johnson announced Friday that its single-shot coronavirus vaccine was 66% effective in protecting against moderate to severe COVID-19 disease in the U.S. and seven other countries, but 57% effective against the South Africa coronavirus variant.

Why it matters: The vaccine is not as effective as some of its two-dose competitors, like Moderna and Pfizer, but still provides strong protection against the most serious COVID-19 symptoms. The company said it will file for emergency use authorization from the FDA within a week.

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