(Bloomberg) -- Two doses and a booster of the Covid-19 vaccine made by China’s Sinovac Biotech Ltd., one of the most widely used in the world, didn’t produce sufficient levels of neutralizing antibodies to protect against the omicron variant, a laboratory study found.  

For those who are fully immunized with the vaccine known as CoronaVac, getting a booster shot from Germany’s BioNTech SE significantly improved protective levels of antibodies against omicron, according to the study from the University of Hong Kong and the Chinese University of Hong Kong. Two doses of the BioNTech shot, known as Comirnaty, was also insufficient, the researchers said in a statement. 

While much is still unknown about how Sinovac’s shot holds up to omicron -- including how T cells, the immune system’s weapon against virus-infected cells, will respond -- the initial results are a blow to those who have received CoronaVac. There have been more than 2.3 billion doses of shot produced and shipped out, mostly in China and the developing world. 

With omicron seen to be about 70 times more transmissible than the delta variant, the prospect of having to roll out a different booster shot or even re-vaccinate with a more omicron-specific vaccine will set back the world’s efforts to exit the pandemic.

The research, led by Malik Peiris and David Hui, examined the production of virus neutralizing antibodies in the blood of people vaccinated with the two shots currently in use in Hong Kong. They confirm two doses of either vaccines weren’t sufficient to fend off omicron. 

The news comes as Hong Kong government’s medical advisers cleared the way for adults in the city to receive a booster shot, no matter which vaccine they initially received. The new study suggests it’s important to get the right one.

Last week, Sinovac released lab studies saying 94% of people getting three doses of its shot had sufficient neutralizing antibodies to omicron, up from 35% when only two doses were given. 

Sinovac Provides Inadequate Shield Against Omicron, Studies Show

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