(REUTERS): Antibodies triggered by Sinovac Biotech’s COVID-19 vaccine fade away after six months, although a third shot could have a strong boosting effect, a lab study has revealed.
The study was conducted by researchers at disease control authorities in Jiangsu province, Sinovac, and other Chinese institutions. The researchers reported the findings from a study of blood samples from healthy adults aged between 18-59.
For participants receiving two doses, two or four weeks apart, only 16.9% and 35.2% respectively still had a level of neutralising antibodies above the threshold six months after the second dose.
Those readings were based on data from two cohorts involving more than 50 participants each, while the study gave third doses to a total of 540 participants.
When participants in some cohorts were given a third dose, about six months after the second, neutralising antibody levels after a further 28 days had increased around 3-5 fold from the levels seen four weeks after the second dose.
Researchers cautioned the study did not test the antibodies’ effect against more transmissible variants, and that further research was needed to assess antibody duration after a third shot.
Earlier this month, Thailand announced it would use AstraZeneca’s Covid-19 vaccine as a second dose for those who received Sinovac’s shot as their first dose in a bid to increase protection.
