Covid-19 vaccines: Sinovac recipients may need two booster shots, says scientist
- A preprint study suggests adding a dose of Pfizer after two shots of the Chinese vaccine boosts protection but was not enough to stop Omicron infection
- Sinovac is widely used in China and developing countries
The findings suggest countries that have used the Pfizer vaccine as a booster dose after Sinovac’s CoronaVac, widely used in China and developing countries, may still need to offer a second booster dose, according to one author of the paper, which has not been peer-reviewed.
The researchers from Yale University analysed plasma samples from 101 participants in the Dominican Republic who received a booster dose of Pfizer’s vaccine more than four weeks after being given a second dose of Sinovac, which is made using inactivated, or dead, matter from the coronavirus to stimulate an immune response.
The results were then compared to samples from 37 health care workers from the Yale-New Haven Hospital who received two doses of Pfizer, made using cutting-edge mRNA technology.
They found that receiving two doses of CoronaVac followed by a Pfizer booster dose elevated the levels of neutralising antibodies 10.1 times against the original Sars-CoV-2 virus and 6.3 times against the Delta variant 28 days after the booster shot.
However, antibody neutralising activity for this combination against the Omicron variant was 6.3 times lower than against the original virus, and 2.7 lower than against the Delta variant.
There was no neutralising activity observed for participants who only received two doses of CoronaVac. Although the level of antibodies was 1.4 times higher than those who had received two doses of the Pfizer mRNA vaccine, this was not enough to protect against Omicron infection.