China's top respiratory disease expert Zhong Nanshan advised on Friday to use a different type of vaccine as a booster following two doses of inactivated vaccines, as using a different vaccine for the booster turned out to be significantly more efficient in the prevention against COVID-19.

Based on the dynamic zero-COVID policy that China will unwaveringly stick to, the infection rate as well as severe illness and mortality rates need to be reduced. Thus, a different type of vaccine for a booster dose, such as a subunit protein or an adenovirus vectored vaccine following two doses of inactivated vaccines, is recommended, Zhang said in a keynote speech he delivered during the 14th China Bioindustry Convention held in Guangzhou, South China’s Guangdong Province between Friday and Sunday. He emphasized that excessive epidemic prevention measures that could negatively impact economic development should not be an option.

China’s current policy is not a simple “dynamic zero-COVID” policy but a policy that strikes a balance between the stability of economy and development and epidemic prevention, Zhong said, adding that focused prevention and control based on scientific management, prevention and treatment is still in need.

According to Zhang, using the same vaccine in the booster immunization proves to have less desired efficacy in the prevention against COVID-19. None of the current COVID-19 vaccines on the market, including the four-dose mRNA vaccines, is effective enough to prevent the infection of the Omicron variant.

“One month after the administration of four doses of mRNA vaccines, the efficacy of prevention against Omicron drops to 11 percent for Moderna or 30 percent for Pfizer mRNA vaccines. The breakthrough infection cases have a high viral load and are highly infectious,” Zhong said.

Zhong explained that so far 38 COVID-19 vaccines classified into five categories including inactivated, adenovirus vectored, subunit protein, mRNA, virus-like particle (VLP) vaccines, have been approved for clinical use by the WHO.

At present, the new vaccines developed in China include subunit protein, second-generation mRNA and inhalation (aerosol, nasal spray) vaccines.
“Domestic second generation sequential mRNA vaccine can significantly improve the neutralization of Omicron variant,” said Zhong, who was jabbed with the domestically produced recombinant protein vaccine produced by Anhui Zhifei Longcom Biopharmaceutical Co Ltd as a booster.

In terms of the treatment for COVID-19, China has developed 3C-like proteases (3CLpro) inhibitors, short interfering RNA (siRNA), and monomer and antibody treatment of traditional Chinese medicine, Zhong said.

The epidemic situation on the Chinese mainland still presents a complex situation with flare-ups in multiple areas, including Beijing, Shanghai and North China’s Inner Mongolia Autonomous Region.

Global Times