A senior Chinese official said that the country’s vaccines may need to be administered in greater doses or in concert with other shots because of their low overall effectiveness.

The comments on Saturday by Gao Fu, the director of China’s disease control center, suggest that China and more than 60 countries that have approved Chinese vaccines could need to adjust their distribution programs. The widespread distribution of Chinese vaccines means that any changes could potentially affect hundreds of millions of people or more.

Possible steps to increase the effectiveness of Chinese vaccines include changing the amount of vaccine given, the number of shots, the time between shots or the type of vaccines given, Mr. Gao said.

He also praised the possibilities offered by messenger RNA. That technology is used in the Moderna and Pfizer-BioNTech vaccines but not in any of the vaccines thus far approved in China.

In an interview on Sunday with the Communist Party-run Global Times newspaper, Mr. Gao said his earlier comments had been misunderstood, and that discussion of how to improve the effectiveness of vaccines should be a universal question.

“The protection rates of all vaccines in the world are sometimes high, and sometimes low,” he said. “How to improve their efficacy is a question that needs to be considered by scientists around the world.”

Officials in Brazil said in January that the efficacy rate for the CoronaVac vaccine from the Beijing-based company Sinovac was just over 50 percent, which is the threshold that the World Health Organization has said would make a vaccine effective for general use. By comparison, Moderna and Pfizer-BioNTech were found to be 90 percent effective in real-world conditions, researchers said last month.

Last month, the distributor in the United Arab Emirates of vaccines from China’s Sinopharm said it was offering a third dose in addition to the standard two-dose regimen for a “very small number” of people who were “not really responsive” to the vaccine.

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