A small-sample Hong Kong research showed that Sinovac’s CoronaVac shot, boosted with a third dose about two to five months after the second, failed to produce neutralising antibody responses to Omicron in most recipients.
The Sinovac booster-triggered antibody response was also weaker against Delta than a CanSinoBIO booster in a clinical trial.
Tested against Omicron in a Chinese study, a third BBIBP-CorV shot produced by Sinopharm elicited lower antibody level than a booster of Zhifei’s vaccine in those who already received two BBIBP-CorV shot.
Among close contacts of infected people in an earlier Omicron outbreak in Chinese cities of Tianjin and Anyang, receiving a booster reduced Omicron breakthrough infection rate more than threefold compared with the primary vaccination, said Shao Yiming, who is on an expert team for China’s COVID vaccine development work group, at Saturday’s news briefing.
Shao did not provide complete data or specify which boosters were analysed for the readings.
Products from Sinopharm and Sinovac approved in China are inactivated vaccines that contain inactivated or “killed” coronavirus. Zhifei’s vaccine contains parts of the coronavirus protein, while the CanSinoBIO shot uses a modified human cold virus to ferry genetic material from the coronavirus protein.
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