A staff member takes out samples of the COVID-19 inactivated vaccine at a vaccine production plant of Sinopharm in Beijing, on April 11, 2020. [Photo/Xinhua]

BEIJING -- Two inactivated vaccines developed by the Chinese pharmaceutical giant Sinopharm have shown to be safe and effective against COVID-19 in phase-3 human trials, according to a study published this week in The Journal of the American Medical Association.

The randomized, double-blind and placebo-controlled trials were designed by the Wuhan Institute of Biological Products Co, Ltd, and the Beijing Institute of Biological Products Co, Ltd, both of which belong to the China National Biotec Group(CNBG), affiliated with Sinopharm.

It is the world's first published phase-3 study results of inactivated COVID-19 vaccines, the CNBG said in a statement on Thursday.

According to the study, more than 40,000 people overseas aged 18 and above were enrolled in the trials. The vaccination procedure included two shots with an interval of 21 days.

The virus strains in the study were isolated from two patients in Wuhan's designated coronavirus-treating Jinyintan Hospital and separately used to develop the two inactivated vaccines.

Fourteen days after inoculation, all vaccine receivers produced high titers of antibodies, and the seroconversion rate of neutralizing antibodies was higher than 99 percent in both vaccine groups, indicating strong immune responses induced by the two vaccines, the study said.

(China Daily)