Delta vaccine: Chinese researchers find Sinovac booster aids immune response to devastating variant

Findings ‘rationalise the use of three-dose immunisation regimens for inactivated vaccines’, according to paper

A number of countries are considering boosters or authorising them for certain groups amid the battle against the Delta variant

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Chinese health officials late last month recommended booster shots for high-risk and vulnerable groups, but said further study was needed before extra jabs were considered for the general public. Photo: STR/AFP

Published: 5:00pm, 7 Sep 2021Updated: 9:56pm, 7 Sep 2021

A third dose of the Covid-19 vaccine by Sinovac Biotech can boost a flagging immune response to the highly transmissible Delta variant, a team of Chinese researchers has found.

Study participants who received a three-dose regimen of the Sinovac shot showed a more than 2½ times higher neutralising ability against Delta four weeks after the last shot, compared with those who received two doses or had recovered from a naturally acquired Covid-19 infection, according to the small-scale study that has not been peer-reviewed.

The researchers – including scientists from the Chinese Academy of Sciences, Peking University and the vaccine maker – said their data also indicated a third dose would allow vaccine protection to last longer.

The findings “rationalise the use of three-dose immunisation regimens for inactivated vaccines”, they wrote in a paper released on the server medRvix on Sunday.

“Our results demonstrate that a third-dose booster of inactivated vaccine can elicit an expeditious, robust and long-lasting recall humoral [immune] response,” they wrote.

Chinese health officials late last month recommended booster shots for high-risk and vulnerable groups, but said further study was needed before extra jabs were considered for the general public. Five of the seven vaccines in use domestically use an inactivated platform, which relies on a dead version of the virus to stimulate immune response.

Sinovac’s Covid-19 vaccine is among products headlining the domestic roll-out, which has surpassed 2 billion doses. The two-dose vaccine is also widely used around the world.