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Hong Kong CNN  — 

When the highly infectious Delta variant hit China in the summer, some public health experts were hopeful that the country could soon receive an immunity boost from BioNTech’s highly effective mRNA Covid-19 vaccine.

In July, the shot was reported to have passed an expert review by Chinese regulators and was in the administration review stage, according to Fosun Pharma, the Chinese partner of BioNTech licensed to produce and distribute the vaccine in the Greater China region. Fosun was even planning to start domestic trial production by the end of August.

However, five months later there is still no word from Chinese officials on when – or whether – the vaccine will ever be approved, even as the newly emerged Omicron variant is detected in China, posing a fresh challenge to the country’s zero-Covid strategy and its less effective domestic vaccines.

Health authorities in the northern port city of Tianjin have detected mainland China’s first case of the Omicron variant among inbound travelers who arrived from overseas on December 9, state media reported Monday.

Much remains unknown about the fast-spreading Omicron variant, which carries an unusually large amount of mutations that scientists worry could potentially make it more transmissible and less susceptible to existing vaccines.

Preliminary lab studies show two doses of the BioNTech vaccine, which is produced by Pfizer outside of China, may not provide sufficient protection against infection with Omicron, but three doses are able to neutralize it, Pfizer/BioNTech said in a news release last week. Two doses may still provide protection against severe disease, it added.

China has not released studies on how much its domestic vaccines protect against Omicron, though experts and state media have voiced confidence in curbing the new variant.