Fourth Sinopharm shot won’t boost protection against Omicron, study finds

Immunity wanes six months after three doses of the Sinopharm Covid-19 vaccine are given, but a fourth shot will not provide more protection against the Omicron strain, a study has found. Researchers from Sun Yat-sen University in Guangzhou said their study suggested that “urgent use” of inactivated vaccines – like the Sinopharm one – as a fourth booster shot against variants of concern such as Omicron was “feasible but not ideal”. Recombinant spike protein or mRNA vaccines based on the variants of concern would be good alternatives for a fourth booster, they said. The study suggested that immune response could not be endlessly boosted and there would be a “turning point” after repeated vaccination.