Sinovac Vaccine Antibody Levels May Decline In 6 Months, Booster Helps: Study

Coronavirus: Chinese researchers reported the findings from a study of blood samples from healthy adults aged between 18-59. The study has not been peer reviewed.

Antibodies triggered by Sinovac Biotech's COVID-19 vaccine declined below a key threshold from around six months after a second dose for most recipients, but a third shot had a strong booster effect, a lab study showed. Chinese researchers reported the findings from a study of blood samples from healthy adults aged between 18-59 in a paper published on Sunday, which has not been peer reviewed. Among participants who received two doses, two or four weeks apart, only 16.9% and 35.2% respectively still had neutralising antibodies above a threshold set by researchers, below which the antibody level is considered low or undetectable, six months after the second shot, the paper said. Those readings were based on data from two cohorts involving more than 50 participants each, while the study gave third doses of the vaccine or placebo to a total of 540 participants.