In a rare admission of the weakness of Chinese coronavirus vaccines, the country’s top disease control official has said their effectiveness is low and the government is considering mixing them in an attempt to boost their efficacy.
Chinese vaccines “don’t have very high protection rates”, Gao Fu, the director of the China Centers for Disease Control, said at a conference on Saturday in the southwestern city of Chengdu.
Beijing has distributed hundreds of millions of doses in other countries, mostly in Africa, South America and other parts of Asia.
“It’s now under formal consideration whether we should use different vaccines from different technical lines for the immunisation process,” Gao said without specifying whether that would include foreign-made vaccines.
He said changing the number of doses and the length of time between doses were also a “definite” solution to efficacy issues.
The overall effectiveness rate of Sinovac, the most well-known of the four vaccines developed in China for public use, was found to be as low as 50.4 percent during late stage trials in Brazil although the performance was better in Indonesia and Turkey.
The developer has not yet released final data for peer review, but a paper published by Brazilian researchers on Sunday ahead of peer review found two injections of the vaccine when given shorter than three weeks apart, was 49.1 percent effective, below the 50 percent threshold set by World Health Organization.
Data from a small subgroup showed that the efficacy rate increased to 62.3 percent when the doses were given at intervals of three weeks and longer.
In comparison, the vaccine made by Pfizer-BioNTech – also a two dose regimen – has been found to be 97 percent effective.
Beijing has yet to approve any foreign vaccines for use in China, where the coronavirus emerged in late 2019.
Gao gave no details of possible changes in strategy but mentioned mRNA, a previously experimental technique that was used to develop the Pfizer jab and by some other Western vaccine developers. China’s drug-makers have relied on traditional technology.
“Everyone should consider the benefits mRNA vaccines can bring for humanity,” Gao said. “We must follow it carefully and not ignore it just because we already have several types of vaccines already.”
Gao previously raised questions about the safety of mRNA vaccines. He was quoted by the official Xinhua news agency as saying in December he could not rule out negative side effects because they were being used for the first time on healthy people.
Chinese state media and popular health and science blogs also have questioned the safety and effectiveness of the Pfizer-BioNTech vaccine, which uses mRNA.
As of April 2, some 34 million people have received the two doses required by Chinese vaccines and about 65 million received one, according to Gao.
Experts say mixing vaccines, or sequential immunisation, might boost effectiveness rates. Trials around the world are looking at mixing vaccines or giving a booster shot after a longer time period.
Researchers in Britain are studying a possible combination of the Pfizer-BioNTech and AstraZeneca vaccines.
China has shipped millions of its vaccines abroad, and officials and state media have fiercely defended the shots while calling into question the safety and logistics capabilities of other vaccines.
“The global vaccine protection rate test data are both high and low,” Gao told state tabloid Global Times on Sunday.
“How to improve the protection rate of vaccines is a problem that requires global scientists to consider,” Gao said, adding that mixing vaccines and adjusting immunisation methods are solutions that he had proposed.
Gao also rejected claims by some media reports that he said Chinese COVID-19 vaccines have a low protection rate, telling Global Times that it was “a complete misunderstanding.”