The study, which has not been peer-reviewed
yet, was conducted by researchers from Yale University, the Dominican
Republic’s Ministry of Health and other institutions.
The Sinovac two-dose regimen along with the
Pfizer shot produced an antibody response similar to a two-dose mRNA vaccine,
according to the study. Antibody levels against omicron were 6.3-fold lower
when compared with the ancestral variant and 2.7-fold lower when compared with
Akiko Iwasaki, one of the authors of the
study, said on Twitter that CoronaVac recipients may need two additional
booster doses to achieve protective levels needed against omicron.
The two-dose Sinovac vaccine alone did not
show any detectable neutralisation against omicron, according to the study that
analysed plasma samples from 101 participants in the Dominican Republic.
A study from Hong Kong last week said that
even three doses of the Sinovac vaccine did not produce enough antibody
response against omicron and that it had to be boosted by a Pfizer-BioNTech
shot to achieve “protective levels.”
Sinovac’s CoronaVac and state-owned
Sinopharm’s BBIBP-CorV vaccine are the two most-used vaccines in China and the leading
COVID-19 shots exported by the country. Hong Kong has been using the Sinovac
and Pfizer-BioNTech vaccines.