A phase-1 trial using a single dose of a vaccine (Ad5-nCoV) that uses a recombinant adenovirus type-5 vector that carries the genetic material that codes for spike glycoprotein of novel coronavirus was found to be safe, well-tolerated and able to generate immune responses against the virus.
Virus-specific antibodies as well as neutralizing antibodies increased at day 14, peaking at day 28 post-vaccination, and most adverse events were mild to moderate, reported Wei Chen, PhD, of Beijing Institute of Biotechnology, and colleagues writing in The Lancet.
In the USA and United Kingdom, vaccines from Moderna and Oxford University (collaborating with AstaZeneca) are in human trials, and have shown promising early results.
"These results represent an important milestone". However, the researchers mentioned in the study that they don't know for sure how much the vaccine would be protective against COVID-19 since they don't know much about the effectiveness of antibodies and T-cell response against the disease.
Based on the results, Chen said the vaccine is a potential candidate for further investigation.
"These results should be interpreted cautiously".
"The challenges in the development of a Covid-19 vaccine are unprecedented, and the ability to trigger these immune responses does not necessarily indicate that the vaccine will protect humans from Covid-19".
The vaccine, called Ad5-nCoV, is being developed by the Chinese company CanSino Biologics, and was one of the first coronavirus vaccines to enter early human trials back in March. The idea is that a person's immune system will create antibodies against the spike protein, which will help fight off the coronavirus if the person is later exposed to it.
Nine Rhesus Macaque monkeys - similar to this one - were given a trial coronavirus vaccine in a U.S. study that found they were ultimately immunised or resisted re-infection. These are the body's humoral response', which is the part of the immune system that produces antibodies to fight infection, and the "cell-mediated' arm, which depends on a group of T cells to fight the virus, the scientists said". There are now 95 vaccines in development against SARS-CoV-2, with most expected to clear Phase I and two experimental vaccines already moving into Phase II trials. There were no serious adverse events.
Most of the people dosed with the vaccine had immune responses, although their levels of antibodies thought to neutralize the virus were relatively low.
The most common adverse reaction was pain at the injection site (58 participants or 54%), fever (50 participants), fatigue (47 individuals), headache (42 participants) and muscle pain (18 participants).
All dose levels of the vaccine triggered some immune response - antibodies that bind to the coronavirus but do not necessary attack it - within two weeks of the vaccination. Some of the participants, the researchers said, also exhibited a form of neutralising antibodies against SARS-CoV-2.
After 28 days, most participants had a four-fold increase in binding antibodies (35/36, 97% low-dose group; 34/36 (94%) middle-dose group, and 36/36, 100% in high-dose group). "Moreover, high pre-existing Ad5 immunity may also have a negative impact on the persistence of the vaccine-elicited immune responses".
After exposing nine adult macaques to the SARS-CoV-2 virus, the researchers monitored viral levels as the animals recovered.
The study's authors also noted that their research is limited because of its small sample size and short duration, and it also lacked a control group.