The study found that a third dose of the vaccine could have a restorative effect.
Antibodies generated by Sinovac Biotech’s Covid-19 vaccine fall below a key threshold around six months after the second dose in most cases, although a booster could have a restorative effect. according to a laboratory study.
Chinese researchers reported in their findings from the study of blood samples from healthy adults between the ages of 18 and 59, in a report published on Sunday, which has not been peer-reviewed.
For participants who received two doses of Sinovac, two to four weeks apart, only 16.9% and 35.2%, respectively, still had neutralizing antibody levels above the threshold six months after the second dose, the study indicated.
Those readings were based on data from two groups that involved more than 50 participants each, while the study delivered a third dose of the Sinovac vaccine to a total of 540 participants.
When participants in certain groups were given a third dose of Sinovac, approximately six months after the second, the levels of neutralizing antibodies after another 28 days increased about 3 to 5 times from the levels observed four weeks after a second dose, research showed.
The study was conducted by researchers from the disease control authorities in Jiangsu province, with experts from Sinovac and other Chinese institutions.
The researchers cautioned that the study did not test the effect of the antibodies against more transmissible variants and that more research was needed to assess the duration of the antibodies after the third injection of Sinovac.