China Zhifei's COVID shot largely retains effect against Delta variant-lab study

COVID-19 vaccine developed by a unit of China's Chongqing Zhifei Biological Products largely retained its neutralising effect against the Delta variant but there was a slight reduction, Chinese researchers found in a laboratory study.

Scientists and regulators are watching closely to see whether the Delta variant, which is significantly more contagious than the original variant of the new coronavirus, will render available vaccines and treatments insufficient.

Tested against particles mimicking the real Delta variant, serum samples from people vaccinated with Zhifei's three-dose regimen showed a 1.2-fold reduction in neutralising effect compared with against particles mimicking an older variant, researchers said in a paper published on Friday without peer review. 

However, researchers cautioned that data from clinical trials or real-world use were still necessary to determine how well the shot can prevent people from getting sick by the variants.

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Efficacy results from the Phase III clinical trial is yet to be published for the vaccine.

The study, where samples from 28 people were collected and tested, also found that samples from those who received their third dose at longer intervals between the second shot showed a greater activity against variants.

Over 100 million doses of Zhifei's vaccine, dubbed ZF2001 and approved for emergency use in China and Uzbekistan, have been administered, the paper said.

Authors of the paper include researchers from Institute of Microbiology at Chinese Academy of Sciences, which is jointly developing the vaccine with Zhifei's unit, and other Chinese institutions.