Experts say mixing vaccines,or sequential immunisation,might boost effectiveness. Researchers in Britain are studying a possible combination of Pfizer-BioNTech and the traditional AstraZeneca vaccine.
The coronavirus pandemic,which began in central China in late 2019,marks the first time the Chinese drug industry has played a role in responding to a global health emergency.
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Vaccines made bySinovac,a private company,andSinopharm,a state-owned firm,have made up the majority of Chinese vaccines distributed to several dozen countries including Mexico,Turkey,Indonesia,Hungary,Brazil and Turkey.
The effectiveness of a Sinovac vaccine at preventing symptomatic infections was found to be as low as 50.4 per cent by researchers in Brazil,near the 50 per cent threshold at which health experts say a vaccine is useful. By comparison,the Pfizer-BioNTech vaccine has been found to be 97 per cent effective.
Health experts say Chinese vaccines are unlikely to be sold to the United States,western Europe and Japan due to the complexity of the approval process.
A Sinovac spokesman,Liu Peicheng,acknowledged varying levels of effectiveness have been found but said that could be due to the age of people in a study,the strain of virus and other factors.
Beijing has yet to approve any foreign vaccines for use in China.
Gao previously questioned the safety of mRNA vaccines. He was quoted by the official Xinhua News Agency as saying in December he couldn’t 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.
Gao also said that taking steps to “optimise” the vaccine process including changing the number of doses and the length of time between doses was a “definite” solution to the efficacy issues.
“Inoculation using vaccines of different technical lines is being considered,” he said.
As of April 2,some 34 million people in China have received both of the two doses required for Chinese vaccines and about 65 million received one,according to Gao.
“The global vaccine protection rate test data are both high and low,” Gao told state tabloidGlobal Times on Sunday.
“How to improve the protection rate of vaccines is a problem that requires global scientists to consider,” Gao said.
The Sinovac spokesman,Liu,said studies find protection “may be better” if time between vaccinations is longer than the current 14 days but gave no indication that might be made standard practice.
AP,Reuters