Two COVID-19 vaccines developed by China's Sinopharm have shown an efficacy of over 72 percent in large scale phase-3 clinical trials, according to a study published in The Journal of the American Medical Association (JAMA) on Wednesday.

The two inactivated vaccines, developed by Sinopharm's Wuhan Institute of Biological Products and Beijing Institute of Biological Products, showed an efficacy of 72.8 percent and 78.1 percent respectively against symptomatic COVID-19 cases, with rare serious adverse effects reported, according to the interim analysis of the ongoing trials.

The randomized, double-blind and placebo-controlled trials were designed by the two institutes, 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 in the United Arab Emirates and Bahrain aged 18 and above without known history of COVID-19 participated in the trials. Study enrollment began on July 16, 2020. Data sets used in the study were locked on December 31, 2020.

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.

The vaccination procedure required two intramuscular injections with an interval of 21 days.

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.

The trials are still ongoing overseas, and long-term efficacy of the two Chinese vaccines for COVID-19 prevention needs to be further evaluated, the study noted.

China has several self-developed COVID-19 vaccines undergoing late-stage clinical trials, and this study is the first to publish the phase-3 trial results of such vaccines. 

(With input from Xinhua)