By Drew Hinshaw and Chao Deng

The World Health Organization endorsed a Covid-19 vaccine developed by the Chinese state-owned firm Sinopharm, clearing the shot for global use and boosting Beijing's bid to play a leading role in the fight against the pandemic.

The international health body recommended that the vaccine be used immediately, as part of an "emergency use listing." It said the drug's deployment would help quickly ease acute vaccine shortages in developing countries that have been unable to inoculate more than a tiny percentage of their populations.

But the authorization came with caveats as the WHO said too little data exists to show whether the vaccine was effective in people over 60.

Still, the WHO panel that reviews vaccines -- its Strategic Advisory Group of Experts -- concluded that preliminary data suggested elderly test subjects likely did acquire some protection against the disease. The panel found no reason to believe that the shot wouldn't be as safe in older age groups as it is in younger demographics. In all adults, 18 and older, the vaccine was 79% effective in preventing symptomatic cases of Covid-19.

"The addition of this vaccine has the potential to rapidly accelerate Covid-19 vaccine access for countries seeking to protect health workers and populations at risk," said Dr. Mariangela Simao, the WHO's assistant director general for access to health products.

The shot comes as a massive spike in Covid-19 cases in India, the world's largest vaccine maker, has upended global supply of badly-needed shots. Export restrictions in India have left the WHO's Covax program -- to vaccinate 20% of the developing world's population -- struggling to obtain supplies.

Yet global health experts have criticized the Chinese government and Chinese vaccine makers, including Sinopharm, for a lack of transparency about their clinical trials and efficacy data. Because China has largely been able to get Covid-19 under control, Sinopharm had to conduct trials abroad, in several different countries at once. WHO officials said that process was challenging, leaving them without sufficient data in older groups.

Sinopharm's vaccine appears to be substantially less effective than the leading Western vaccines against Covid-19. Still, scientists have argued for its use at a time when the global Covid-19 case count is still climbing at a rate of hundreds of thousands per day. Unlike shots from Pfizer Inc. and Moderna Inc., the Sinopharm vaccine doesn't need to be kept at extremely cold temperatures, and a small sticker on its vials changes color if the vaccine has been exposed to excess heat.

The vaccine is the sixth targeting Covid-19 that WHO has granted an emergency use designation, joining candidates by AstraZeneca PLC, Pfizer and Johnson & Johnson. It is the only inactivated virus vaccine to be authorized. The WHO is currently reviewing a second Chinese-made vaccine, by Chinese drugmaker Sinovac Biotech.

Write to Drew Hinshaw at drew.hinshaw@wsj.com and Chao Deng at Chao.Deng@wsj.com

(END) Dow Jones Newswires

05-07-21 1305ET