"We have registered none serious adverse effects on the volunteers during the tests. If everything goes as planned, the projects would finish the second part of their tests in July," the NHC deputy director Zeng Yixin said.
China has five possible vaccines against COVID-19, one of which relies on a viral vector (an adenovirus) to transport parts of the coronavirus and the other four on an inactivated version of the infectious agent causing the pandemic of COVID-19.
According to international medical protocols, in the first phase of the development of a vaccine, the possible medicine is applied to groups of between 20 and 100 healthy people. By doing so, the researchers seek to identify side effects and determine the appropriate dosage.
In the second phase, scientists expand the number of subjects taking part in the tests and administer the potential vaccine to people who respond to the profile of the potential user to assess its efficacy and safety.
In the third phase, thousands of people are involved in the tests and, if everything goes well, health authorities could approve the vaccine, although sometimes a phase four with more in-depth studies is usually carried out.
Typically, the period for a vaccine to be available for use at a mass level is at least 12 to 18 months, according to the World Health Organization (WHO).
Due to the global health emergency, however, China innovated its protocols and allowed first and second phase studies to be conducted at the same time on some potential vaccines.
So far, 2,575 volunteers have taken part in these studies, of whom 539 took part in the first phase and 2,036 in the second one.
"We have preliminary data from the first-phase tests on the safety of vaccines and their ability to create protective antibodies against the coronavirus," Zeng said.
In late April, the Center for Disease Control and Prevention Director Gao Fu indicated that the vaccines under development could be fully ready in early 2021.
However, he also revealed that China could have a vaccine in September to be used in health workers in the event of a new large-scale outbreak.
The development of a COVID-19 vaccine has become a race against time in which international public health is not the only issue at stake.
Earlier this week, President Donald Trump's administration accused Chinese hackers of having carried out cyber-attacks against U.S. research centers to steal information about the vaccines and treatments that are being tested.
In reply to these accusations, Beijing assured that Washington only seeks to divert attention from the incidence of the virus in the United States.