A staff member displays samples of the COVID-19 inactivated vaccine at Sinovac Biotech Ltd, in Beijing, capital of China, March 16, 2020. [Photo/Xinhua] Respecting laws of science fundamental principle in its development, he says Experimental COVID-19 vaccines developed by Chinese researchers are safe, and ongoing efforts to push for their market approval will strictly follow the rules of science, a health official said on Monday. China is conducting third-stage clinical trials for five Chinese-made vaccine candidates overseas and has administered emergency inoculations to nearly 1 million people in the country, according to Zheng Zhongwei, an official with the National Health Commission who is leading the task force on vaccine development. "These vaccinations have fully demonstrated the safety of Chinese-made vaccines. There is some adverse reaction, but no severe adverse effect has been reported," he said during a news conference on Monday. He added that results from third-stage human trials are needed to determine the efficacy of these vaccines, although data from earlier phases of clinical trials and reports from recipients of emergency inoculations in high-risk countries have already shown the protective effects of these doses. "Some leading developers have just obtained enough cases to conduct analysis of its efficacy. They have begun to submit materials needed for approval to the National Medical Products Administration," Zheng said. Market approval will only be granted after submitted trial findings meet the requirements of the top drug regulator, he added. Zheng stressed that throughout the vaccine development process in China, respecting the laws of science has always been the fundamental principle. "I believe that after third-stage trial results are revealed, the drug regulator will advance the registration and approval procedures at a relatively fast pace," he said. "Some manufacturers are also gearing up for mass production." China has been in a leading position in the global race for a COVID-19 vaccine. As of Dec 2, a total of 15 Chinese-made vaccines employing five different technologies have entered clinical trials, according to Zheng. Three inactivated vaccines－two developed by Sinopharm and one by Sinovac－were among the first candidates in the world to begin the third and late stage of clinical trials, according to Zheng. The fourth inactivated vaccine created by the Chinese Academy of Medical Sciences' Institute of Medical Biology in Kunming, Yunnan province, has recently passed ethical reviews in foreign countries and is about to begin the third-stage trial. Third-stage trials of the adenovirus vaccine in Russia, Pakistan and Mexico have enrolled over 20,000 people, and the recombinant protein vaccine is being tested in Uzbekistan, he said. Chinese health officials said over the weekend that in a two-stage vaccination drive, the country will first focus on vaccinating all people at high risk of contracting the virus over the winter and spring. Inoculation program Zheng said the emergency inoculation program mainly covers cold-chain workers, border control personnel, front-line medical and disease control workers and people going abroad for work. Since its official launch in July, authorities have gradually expanded the scope of the program and have been prudent and careful. All people receiving the doses were voluntarily inoculated, he said. He added that local governments are now evaluating the number of people that are expected to participate in the program in the winter and spring. When a vaccine is eventually released for public use, it is estimated that 70 percent of the population will have to be vaccinated in order to build up herd immunity, which will stamp out the virus, Wang Huaqing, a chief researcher at the Chinese Center for Disease Control and Prevention, said on Monday. He added that before herd immunity is established, the public is urged to stick to personal protective measures, such as mask-wearing and keeping social distance.