(Reuters) – A third booster dose of a COVID-19 vaccine made by either AstraZeneca, Pfizer-BioNTech or Johnson & Johnson increases antibody levels significantly in those who have previously received two doses of Sinovac’s CoronaVac shot, a study has found.

The study found that CoronaVac received the strongest boost from a viral-vector or mRNA shot, including against the Delta and Omicron coronavirus variants, researchers from Brazil and Oxford University said in a press release on Monday.

China-based Sinovac’s vaccine uses an inactivated whole coronavirus strain that was isolated from a patient in China, plus a standard adjuvant. It is currently approved in more than 50 countries including Brazil, China, Argentina, South Africa, Oman, Malaysia, Indonesia and Turkey.

“This study provides important options for policymakers in the many countries where inactivated vaccines … have been used,” said Andrew Pollard, director of the Oxford Vaccine Group and study lead.

However, another study in December found that Sinovac’s two-dose shot followed by a booster dose of Pfizer-BioNTech’s vaccine generated less of a neutralising immune response against the Omicron variant compared with other strains.

A third dose of CoronaVac also increased antibodies, but the results were better when a different vaccine was used, according to the latest study that included 1,240 volunteers from the Brazilian cities of Sao Paulo and Salvador.

SOURCE: https://bit.ly/3GZt4AS The Lancet, online January 21, 2022.

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