Colorized scanning electron micrograph of an apoptotic cell (blue) infected with SARS-COV-2 virus particles (red), also known as novel coronavirus, isolated from a patient sample. Image captured at the NIAID Integrated Research Facility (IRF) in Fort Detrick, Maryland. Photo: National Institute of Allergy and Infectious Diseases, NIH/Handout via REUTERS.

Chinese researchers have started a second phase human trial of a possible coronavirus vaccine, the Institute of Medical Biology at Chinese Academy of Medical Sciences (IMBCAMS) said on Sunday, in efforts to further assess effectiveness and safety.

About a dozen vaccines are in different stages of human tests globally, as the World Health Organization warns the coronavirus pandemic is accelerating and “the world is in a new and dangerous phase.”

However, none of the vaccine trials have passed large-scale, late-stage phase 3 clinical trials, a necessary step before getting regulatory approval for sale.

IMBCAMS began on Saturday a phase 2 human test for its experimental shot, which is among six possible vaccines Chinese scientists are testing in humans, following an on-going phase-1 study that has recruited about 200 participants since May, the institute said on Sunday in its social media channel.

The phase-2 trial will determine the shot’s dose and continue to evaluate whether the potential vaccine can safely trigger immune responses in healthy people.

IMBCAMS said it expects to use a plant dedicated to producing a coronavirus vaccine this year to prepare for China’s future vaccine supplies.

As early as by the end of 2020, certain groups of people with special needs can use experimental vaccines under urgent circumstances, Gao Fu, director at the Chinese Center for Disease Control and Prevention, said last month.

The coronavirus, which was first detected in China late in 2019, has infected 8.81 million people globally and killed more than 460,000 people.