A global study of nearly 44,000 found that the COVID-19 vaccine made by Johnson & Johnson is 66% effective in preventing moderate to severe disease.

The study was conducted in the U.S., Latin America and South Africa. The vaccine did better at preventing disease in the U.S. – 72% — and less well in South Africa – 57% efficacy. The efficacy seen in Latin America was 66%.

The South African results are troubling because of the coronavirus variant spreading there that has now been detected in the U.S., raising concerns that the vaccines developed so far might not work as well against it.

The vaccine did demonstrate complete protection against COVID-19 serious enough to require hospitalization, according to a news release from the company. The vaccine was 85% effective in preventing severe forms of the disease.

The company says it plans to apply to the Food and Drug Administration for emergency use authorization to distribute the vaccine.

The Johnson & Johnson vaccine is given as a single shot, unlike the vaccines from Moderna and Pfizer that require two shots given weeks apart. Also, the Johnson & Johnson vaccine doesn't require ultracold storage.

"These topline results with a single-shot COVID-19 vaccine candidate represent a promising moment," said a statement by Dr. Paul Stoffels, chief scientific officer at Johnson & Johnson. "A one-shot vaccine is considered by the World Health Organization to be the best option in pandemic settings, enhancing access, distribution and compliance."

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