Interim results of phase one and two trials published in the Journal of the American Medical Association suggest a coronavirus vaccine developed by the Chinese pharmaceutical company Sinopharm is safe and induces an immune response.
However, researchers said more study is needed to know whether the vaccine protects people against the virus.
The phase one trial, conducted in Henan Province, China, involved 96 people given high, medium or low doses of the vaccine, or a placebo, which does nothing. The Phase 2 trial, involved 224 adults given the medium dose of the vaccine, or a placebo.
Within seven days after injection, adverse reactions were reported in 15% of trial participants. The most common adverse reaction was injection site pain, followed by fever. All adverse reactions were mild and did not require any treatment.
In the phase two study, the vaccine prompted a neutralizing antibody response in 97.6% of participants. The researchers found that participants had greater neutralizing antibody responses when they were given the second dose of the vaccine three weeks after the first dose rather than two weeks after the first dose.
"My impressions is that they are getting reasonable levels of virus neutralizing antibodies," Dr. Peter Hotez, a vaccinologist at Baylor College of Medicine and a CNN medical analyst, said. "Based on this and safety profile, I believe that this is definitely a vaccine worth pursuing in Phase three clinical trials. I also think that this could be as good as the Operation Warp Speed vaccines in terms of efficacy and safety, but we really need those large trials."
Some background: The US government is supporting six vaccine candidates so far through the Trump administration's Operation Warp Speed program. Two have moved into large, phase three trials on tens of thousands in the United States.
There are 29 vaccines in clinical trials worldwide, according to the World Health Organization.