The Sinovac covid vaccine, of two doses, followed by a booster injection of Pfizer-BioNTech, showed a decreased immune response against Omicron variant compared to other mutations, according to a study by researchers.
The study, which has not yet been peer-reviewed, was conducted by researchers from Yale University, the Dominican Republic’s Ministry of Health, and other institutions.
The two-dose Sinovac regimen in conjunction with the Pfizer injection produced a Antibody response similar to that of a two-dose mRNA vaccine, according to the study. Levels of Omicron antibodies were 6.3 times lower compared to the original variant and 2.7 times smaller compared to Delta.
Akiko Iwasaki, one of the study’s authors, said on Twitter that the CoronaVac recipients may need two additional booster doses to achieve the necessary levels of protection against omicron.
In terms of public health, CoronaVac 2x is insufficient to neutralize Omicron. Even with CoronaVac 2x plus Pfizer booster, NAb is only 1.4x higher than 2x mRNA alone. Thus, CoronaVac recipients may need 2 additional booster doses to reach levels needed against Omicron. (10/) pic.twitter.com/fkTy9aL6eh
– Prof. Akiko Iwasaki (@VirusesImmunity) December 30, 2021
The two-dose Sinovac vaccine alone showed no detectable neutralization against Omicron, according to the study that analyzed plasma samples from 101 participants in the Dominican Republic.
A study conducted last week in Hong Kong noted that even three doses of Sinovac vaccine did not produce a sufficient antibody response against Omicron and that it had to be reinforced with an injection of Pfizer-BioNTech to achieve “levels of protection.”
The CoronaVac vaccine from Sinovac and the BBIBP-CorV vaccine from the state-owned company Sinopharm are the two most widely used vaccines in China and the main covid-19 injections exported by the country. Hong Kong has been using vaccines from Sinovac and Pfizer-BioNTech.
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