Samples of the COVID-19 inactivated vaccine are seen at a vaccine production plant of China National Pharmaceutical Group (Sinopharm) in Beijing, capital of China, April 10, 2020.Photo:Xinhua

 As scientists globally race to develop effective COVID-19 vaccines, scientists from Hong Kong and Macao special administrative regions announced a breakthrough in developing a recombinant COVID-19 vaccine on Monday, indicating that the mass production of the vaccine is feasible at a low cost in the future. 

They have evaluated the potential of a candidate vaccine based on the receptor-binding domain (RBD) of SARS-CoV-2, and found that a recombinant vaccine could induce a potent functional antibody response in immunized mice, rabbits and non-human primates as early as seven to 14 days after a single dose. 

The research, conducted by the Hong Kong Polytechnic University (PolyU) and the Macau University of Science and Technology (M.U.S.T.) in collaboration with Chinese mainland institutions, was recently published in the scientific journal Nature, in a paper entitled, "A vaccine targeting the RBD of the S protein of SARS-CoV-2 induces protective immunity."

Zhang Kang, a professor from the Faculty of Medicine of M.U.S.T., the author of the study, said at Monday's press conference that the biotechnology method used in creating the recombinant vaccine is mature, as many vaccines on the market, such as human papillomavirus (HPV) and flu vaccines, adopted the same method, and that makes the recombinant vaccine feasible for mass production. 

"Manufacturing the most vaccines at the least cost is a key issue in vaccine production, and this vaccine could be mass produced at a low cost," Zhang said. He said that the vaccine will be available in Hong Kong, Macao and other regions and countries. 

Johnson Lau, adjunct professor of the Department of Applied Biology and Chemical Technology at PolyU, told the Global Times at the press conference that the team has started engaging with several collaborators for mass production, and some contracts have been signed. 

The vaccine will start human clinical trials in "at most months, if not weeks," Lau said. 

Five Chinese COVID-19 vaccines have entered the clinical trial stage - one adenovirus vector vaccine and four inactivated vaccines - accounting for 40 percent of clinical-stage vaccines worldwide, according to the Ministry of Science and Technology.

Tao Lina, a Shanghai-based vaccine researcher, told the Global Times on Monday that some domestically made COVID-19 vaccines have entered phase three clinical trials, which usually takes about two to three months. These vaccines may be available for mass production by the end of the year, he said. 

Recombinant vaccines are much easier to be mass produced at a lower cost compared to inactivated vaccines, Tao said. 

Russia plans to launch a mass vaccination campaign in October, and the US company Moderna announced in late July it began phase three trials of a COVID-19 vaccine in the US. 

Reuters reported on Friday, citing an unnamed US security official, that China-backed hackers tried to steal "valuable data" from Moderna. 

Tao said such allegations are purely "nonsense," as many Western vaccine companies including Moderna used the gene sequencing date published by China to develop their vaccines.