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Chinese coronavirus vaccines
ChinaScience

Omicron: China’s Sinovac says third shot could help fight variant, as Hong Kong study fails to reveal antibodies with two

  • About 94 per cent of people with a third dose had detectable levels of antibodies, Sinovac says, after HKU study finds none in 25 people on two-dose regimen
  • The Pfizer-BioNTech vaccine also showed a ‘significant’ immune response drop and boosters may be needed for both, researchers said

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A high school student receives the Sinovac Covid-19 vaccine in Nanjing, in China’s eastern Jiangsu province. Photo: AFP
Simone McCarthy
The Covid-19 vaccine by Sinovac Biotech is not able to produce adequate antibodies to neutralise the highly mutated coronavirus strain Omicron, according to new research from the University of Hong Kong.
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Both the Sinovac vaccine and another by Pfizer-BioNTech produced “inadequate” antibody responses to the variant, HKU scientists said in a statement on Tuesday night, calling for the use of boosters to potentially enhance protection.

Beijing-based Sinovac on Wednesday responded with a statement saying a third shot of its CoronaVac vaccine could improve its ability to neutralise Omicron, citing its own laboratory studies.

The company did not provide details on the levels of virus-fighting antibodies produced or how long after vaccination the measurements were taken, but said some 94 per cent – or 45 out of 48 – people who had taken a third dose had detectable levels.

Roughly seven out of 20 were able to produce detectable antibodies against Omicron after the typical two-dose regimen, Sinovac said.

While it is difficult to compare studies which may use different methods, the company’s findings contrasted with those released on Tuesday in a preprint paper by the HKU researchers.

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The university study also examined neutralising antibodies, one arm of immune response that serves as a rough marker for protection against infection.

Of 25 people who received a full two-dose course of CoronaVac, none were found to have detectable levels of neutralising antibodies, according to study author and top infectious disease expert Yuen Kwok-yung and his team.

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