China could reach herd immunity against Covid-19 by end of year, Zhong Nanshan says

Leading respiratory disease expert says more than 80 per cent of the population is expected to be fully vaccinated by then

Zhong says booster shots could strengthen efficacy of vaccines, citing follow-up study on early stage Sinovac trials

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Respiratory disease expert Zhong Nanshan said Covid-19 vaccines were less effective six months after the first dose, but herd immunity was still achievable with booster shots. Photo: Handout

Published: 10:08pm, 20 Aug 2021Updated: 11:06pm, 20 Aug 2021

China’s top respiratory disease expert Zhong Nanshan on Friday said the country could reach herd immunity against Covid-19 by the end of the year if more than 80 per cent of the population is fully vaccinated.

He said while Covid-19 vaccines, including Chinese ones, were less effective six months after the first dose, herd immunity was still achievable with booster shots.

“[At this stage] we believe a booster shot could strengthen the efficacy of the vaccines and we estimate more than 80 per cent of the population will be vaccinated by the end of this year. Therefore we hope that we will be able to achieve herd immunity [by then],” Zhong told a China-Arab states conference in the Ningxia Hui region via video link.

That forecast was based on data showing that Chinese vaccines had an average efficacy of around 70 per cent, he said.

Zhong also cited a follow-up study on Sinovac’s early stage clinical trials that found a twentyfold increase in neutralising antibody levels – indicating immune response – in people who were given a third dose of the Sinovac jab, nine months after their second. In elderly people it went up 30 times.

China has not yet announced a policy on booster shots. Photo: AFP

A study published last month, co-led by Sinovac, found that a third dose of the vaccine given six or more months after the second jab could boost the concentration of antibodies by three to five times. Antibody levels were found to have declined substantially six months after two doses were given, but the study concluded that a third dose resulted in a “strong boost in immune response”. The research has not been peer-reviewed and was posted on preprint server medRxiv.org.