TAIPEI, Taiwan — The head of the Chinese Center for Disease Control and Prevention conceded that the efficacy of Chinese coronavirus vaccines is “not high” and that they may require improvements, marking a rare admission from a government that has staked its international credibility on its doses.

The comments on Saturday from George Gao come after the government has already distributed hundreds of millions of doses to other countries, even though the rollout has been dogged by questions over why Chinese pharmaceutical firms have not released detailed clinical trial data about the vaccines’ efficacy.

China has struck deals to supply many of its allies and economic partners in the developing world and boasted that world leaders — including in Indonesia, Pakistan and the United Arab Emirates — have taken the shots.

There have been signs that some countries remain skeptical: The UAE recently experimented with administering three shots of the Chinese Sinopharm vaccine, instead of two, over reports of low numbers of antibodies produced in some people, while Singapore has stockpiled but not used Sinovac shots.

China is “formally considering” options to change its vaccines to “solve the problem that the efficacy of the existing vaccines is not high,” Gao said at a conference in Chengdu.

Gao added that one possibility was to adjust the dosage or increase the number of doses. He said another option was to mix vaccines that are made with different technologies, in an apparent admission that China needs to develop messenger RNA vaccines using the revolutionary genetic technology that Western countries have harnessed.


Gao’s remarks, which appeared inadvertent and quickly spread through Chinese social media on Saturday before being mostly censored, marked a departure from the rosy assessments of Chinese-made vaccines by the government. By Sunday, internet users were intentionally misspelling words in their posts while discussing Gao’s comments to keep them from being removed.

Sinopharm and Sinovac use a conventional method of producing vaccines that contains inactivated germs, while other countries’ offerings, including those by Pfizer-BioNTech and Moderna, rely on a newfangled technique that uses messenger RNA (mRNA) to stimulate an immune response.

The mRNA vaccines are widely accepted as having higher efficacy rates, and Chinese pharmaceutical executives have said they are racing to catch up and master mRNA technology themselves.

The admission by the head of the Chinese CDC undercut other arms of the government, including its propaganda organs and diplomats, who have spent months touting Chinese vaccines as part of a soft power push while aggressively sowing doubt about Western alternatives by questioning the efficacy and safety of mRNA technology.

On Sunday, the Global Times, a state-run newspaper that has led the way in pushing theories about the coronavirus originating from outside China, hit back at the “hyped up” reports of Gao’s comments.

It quoted Gao as saying that his comments had been misunderstood and that he was speaking in general terms about how scientists, internationally, should improve their vaccine development.


“I was struck by what Gao said, not because it is significantly different from what we have already known but because it deviates from the official narrative on the effectiveness of Chinese and Western vaccines,” said Yanzhong Huang, a senior fellow at the Council on Foreign Relations. “I think he was trying to push for the approval of the use of Pfizer-BioNTech vaccines in China and/or the acceleration of the development of China’s own mRNA vaccines.”

Even before Gao’s comments, there have been discussion about whether the Chinese companies should tweak their formulations or vaccination regimen. Executives at Sinopharm, the state pharmaceutical giant, said in March that they were assessing whether to include a third booster shot as part of their vaccine’s standard administering procedure. The company said last week that it would begin clinical tests on a third vaccine.

More than 60 countries have approved at least one of China’s vaccines for use. They have been in high demand, especially among lower-income countries, which have not been able to acquire the other vaccines.

Sinopharm has reported a 79 percent efficacy rate for its vaccine — without releasing any data — while trials for Sinovac in Brazil and Turkey have shown an efficacy rate of just 50 percent and more than 80 percent, respectively.

Yet even though both drugmakers carried out mass clinical trials earlier than most other pharmaceutical companies last year, the data has not been still not been published in a peer-reviewed journal.

Foreigners traveling to China, however, have been encouraged to use these Chinese-made vaccines to enjoy streamlined access into the country.


In Turkey, where the Sinovac is in wide use, there has been little concern about the effectiveness of the vaccine. Rather, the worry has been that China won’t be able to deliver the promised 100 million doses amid delays in shipments.

Brazil, Egypt and other nations also have been clamoring for more doses as China has throttled back exports in the face of domestic demand even as cases have been surging worldwide.

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The Washington Post’s Paul Schemm in Dubai contributed to this report.