SINOVAC obtained the sample of the Omicron variant in early December 2021 and then actively promoted research and development of its inactivated COVID-19 vaccine (Omicron specific strain). Preclinical research demonstrated that the vaccine is safe and effective in animals. The Omicron strain booster immunization clinical trial was then approved by the HKU GHK Institutional Review Board (IRB) on 12th April 22 and by the Pharmacy and Poisons Board of Hong Kong on 14th April 22, allowing the carrying out of the clinical study on boosting the immunity of people against the new coronavirus strain in Hong Kong.