Strong effectiveness

"The effectiveness of CoronaVac on the populations where this vaccine has been used is a ray of hope guiding a way out of this public health emergency," Palacios said. "The results from our study in Serrana were particularly outstanding in terms of the increased effectiveness due to the collective immunity elicited by the large scale vaccination with CoronaVac."

The study of 40,300 participants in the United Arab Emirates and Bahrain found one vaccine-developed by Sinopharm subsidiary China National Biotech Group and the Wuhan Institute of Virology-was 72.8 percent effective at preventing symptomatic infection. The other vaccine-made by Sinopharm and Beijing Institute of Biological Products-was 78.1 percent effective. The latter vaccine was listed for emergency use by WHO last month, meanwhile China National Biotech Group has registered an application for WHO for an emergency use listing.

"The overall efficacy is not as great as was seen in the mRNA vaccine trials but is still very good and well above the target level of 60 percent efficacy-even 50 percent could be valuable in a pandemic," Stephen Evans, a professor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine who was not involved in the study, told China Daily.

Pan An, a professor of epidemiology at Huazhong University of Science and Technology, who was involved in the study, said that both of these vaccines are well-suited to combating the pandemic, especially in poorer regions.

"These inactivated vaccines also have the advantage of being easily stored and shipped in 2 to 8 degrees Celsius for years, making them suitable for many developing countries and places with limited cold storage capacity," Pan told China Daily. "China is supplying more and more vaccines to the global market and contributes to the global fight against the pandemic."

The trial involved mostly younger men, so it could not provide an accurate look at the vaccines' ability to prevent severe disease. Pan said Phase III trials involving more at-risk groups are already underway, meanwhile real-world data from national health authorities suggests that Sinopharm vaccines are likely to have a protective effect in older people.

Sinopharm vaccines are already widely in use in countries whose own authorities granted approval ahead of the WHO. And the publication of such "robust "late-stage trial data will provide a further boost of confidence in the treatments, said Andrew Catchpole, chief scientific officer at London-based vaccine testing laboratory hVIVO.