A Chinese study looking at mixing Covid-19 vaccines has shown that receiving a booster shot of CanSino Biologics' vaccine after one or two doses of Sinovac Biotech's vaccine yields a much stronger antibody response than using the Sinovac shot as a booster.

The study, among the first analyses in China combing different Covid-19 vaccines, comes as the country says it will use booster shots in specific groups amid concerns over vaccines' waning protection over time.

Participants who received a CanSinoBio booster dose three to six months after a second Sinovac shot showed a 78-fold jump on average in neutralising antibody levels two weeks later, according to a paper published before a peer review.

By contrast, those who received a Sinovac booster shot showed a 15.2 fold increase in neutralising antibody levels, researchers from local disease control authorities, CanSinoBIO and other Chinese institutions said in the paper.

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