BEIJING, May 27 (Xinhua) -- 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.
The two inactivated vaccines showed 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.
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 advance-stage clinical trials, and this study is the first to publish the phase-3 trial results of such vaccines.