Barely a week after Chinese scientists finished injecting an experimental coronavirus vaccine into their first group of volunteers, official news outlets reported Thursday that a second batch of participants was being recruited.
The trial program is recruiting 500 people, age 18 or older, who reside in Hubei province, the former epicenter of the coronavirus outbreak. Researchers are also trying to establish a placebo control group, according to a statement posted on Weibo, a Twitter-like social media site by state-run newspaper People's Daily.
Developing vaccines requires testing them in three or four phases of a clinical trial, in which an increasing number of people are given the vaccine and then closely observed to gauge side effects and effectiveness. Clinical trials can take years, but in the current pandemic, the timetable is expected to move more quickly.
"It would be a very rapid initiation of the Phase 2 trial," said Mark Slifka, an immunologist who specializes in vaccine studies at the Oregon National Primate Research Center in Beaverton. "It shows that China can move very quickly, very well-organized."
China commenced a Phase I clinical trial on March 16, the same day a Seattle resident received an experimental vaccine made by U.S.-based biotechnology company Moderna Therapeutics.
Beijing's clinical trial, which ended the vaccine to 108 subjects on April 2, is being carried out by a research team led by Chen Wei, a virologist in China's military.
Chen's team and Moderna appear to be the first to launch small clinical trials of vaccines to see whether they are safe and can trigger immune responses.
China reported recently that some of the volunteers for the Phase 1 trial ended their 14-day isolation and observation period, and their CT examinations and blood tests were normal. But authorities have not yet released a full report on their treatment.
If Phases 1 and 2 are considered successful, researchers would be expected to launch Phase 3, which involves administering the vaccine to thousands of people.
As China reports fewer coronavirus infections, medical authorities have indicated the experimental vaccine may be tested abroad.
"If the initial results prove the vaccine is safe and produces [desired] effects, we will continue to test its effectiveness overseas through international cooperation if the global epidemic continues to spread," Chen was quoted as saying in the China Daily earlier this month.
Chinese researchers generally have been more optimistic about the timetable for developing a vaccine than their foreign counterparts.
Wu Zunyou, chief expert in epidemiology at the Chinese Center for Disease Control and Prevention, said last month that it may take China only six months to determine if its vaccine is effective and safe.
On the other hand, public health officials around the world have been warning that a COVID-19 vaccine will not be available to the public for at least 12 to 18 months.