A staff member tests samples of the COVID-19 inactivated vaccine at a vaccine production plant of China National Pharmaceutical Group (Sinopharm) in Beijing, capital of China, April 11, 2020. (Xinhua/Zhang Yuwei)

BEIJING -- China's inactivated COVID-19 vaccine entered the second phase of clinical trial on April 24, according to its developers.

The inactivated vaccine developed by Wuhan Institute of Biological Products under the China National Pharmaceutical Group (Sinopharm) and the Wuhan Institute of Virology under the Chinese Academy of Sciences started its clinical trial on April 12.

Sinopharm said in an announcement that 96 persons in three age groups have received the vaccine in the first phase of clinical trial as of April 23. The vaccine has shown good safety so far and vaccine receivers are still under observation.

The randomized, double-blind and placebo-controlled clinical trials of the inactivated vaccine are conducted in Jiaozuo, central China's Henan Province, and the second phase of clinical trial will focus on the vaccination procedure, according to Sinopharm.

Both the first and the second phase of clinical trials of the vaccine has been approved by the National Medical Products Administration through a green channel.

Sinopharm said the vaccine will also go through the third phase of the clinical trial, and it may take about one year to complete the clinical trial and finally reach the conclusion on the vaccine's safety and efficacy.

China has approved three COVID-19 vaccine candidates for clinical trials. An adenovirus vector vaccine was the first COVID-19 vaccine in the world that has entered the second phase of clinical trial.