Four Chinese vaccine candidates have entered international phase-3 clinical trials so far, said Tian Baoguo with the Ministry of Science and Technology at a news conference in Beijing. All trials are progressing well, he said, with initial indications that the vaccines are safe.

According to Tian, the most common adverse reactions in phase-3 clinical trials are pain and swelling at the injection site, followed by fever, both of which are mild.

The two inactivated vaccines developed by China National Biotec Group (CNBG), which is affiliated to Sinopharm, and the Wuhan Institute of Biological Products, have started phase-3 clinical trials in 10 countries, with more than 50,000 volunteers taking part, said Liu Jingzhen, chairman of Sinopharm.

Sinovac Biotech, another vaccine developer, said that the company's partners in Brazil, Indonesia and Turkey have established monitoring systems for adverse reactions in accordance with internationally accepted standards. So far, no severe adverse reactions related to COVID-19 vaccines have been reported.