China has conditionally approved the registration application of a self-developed recombinant protein subunit vaccine against COVID-19, the National Medical Products Administration said Wednesday.

The vaccine, using purified pieces of the virus' protein to trigger an immune response, is made by recombining the S-protein receptor binding domain (RBD) gene with a gene in Chinese hamster ovary (CHO) cells. The CHO cells make RBD protein dimer that are purified and concentrated for use in producing the vaccine. Aluminum hydroxide adjuvant is added to improve immunogenicity.

Developed by Anhui Zhifei Longcom Biopharmaceutical Co., Ltd., the vaccine was allowed to enter the market on a conditional basis, said the administration, marking the first approved COVID-19 recombinant protein subunit vaccine in China.

In total, five COVID-19 vaccines have been approved for public use in China so far.

(With input from Xinhua)