The race is on. Countries, companies, and scientists are now working to find as soon as possible a vaccine to tackle the coronavirus epidemic. While it might take a while to get there, some initial tests are showing promising results.

There are more than 100 vaccines in development worldwide and among them, some have started or will soon start clinical trials. A company called Moderna was the first one to test a vaccine in people, reporting last week that its first phase clinical trial showed that the vaccine was safe and able to stimulate an immune response.

Now, a team of Chinese researchers carried out a safety trial of a vaccine using a harmless virus modified to carry one of the coronavirus genes. There were side effects but all the participants that got the vaccine had a strong antibody response, including some antibodies that neutralized the virus

The researchers engineered the gene that encodes the spike protein into a harmless virus called Adenovirus 5. Then they produced large amounts of the virus and injected it into a group of people. Despite adenoviruses are not related to coronaviruses, the cells that the engineered infect will still produce the coronavirus spike protein – exposing the immune system to it.

The study was done in Wuhan, Hubei province, which was the centre of the COVID-19 epidemic in China. People living in the city of Wuhan had a much higher risk of SARS-CoV-2 infection compared with those living in other cities outside of Hubei province.

A total of 195 individuals were screened for eligibility in the study. Then 108 participants (51% male, 49% female) were recruited and received the low dose, middle dose, or high dose of the vaccine. Under half of them had side effects such as inflammation, fever and fatigue – what usually comes after the injection of a virus.

None of the side effects were considered serious, with all the participants staying with the study through its 28-day checkup. However, the researchers also found that having a strong immune memory of adenovirus 5 reduced the immune system’s response to the spike protein a bit, which might turn out to be problematic.

The researchers did sensitive tests on the participants to track if the injection induced the production of antibodies. After 14 days from the vaccine’s injection, antibodies against the coronavirus spike protein were apparent. Then, by 28 days, all but three of the participants of the study had large increases in the level of antibodies.

The participants that received a high dose of vaccine injection experienced a response that was over double that of those who got the low dose, with the medium dose falling in between. There was also a T cell response to the spike protein, which is important for a strong overall immune response.

While this is good news, it’s still too early to call it a victory. Neutralizing a virus in culture is very different from neutralizing it in an actual organism. In the past, there have been cases where a vaccine that induced antibodies actually made it easier for the virus to infect cells. That means we don’t know yet if the antibody response will mean protection against the coronavirus.

The findings join other studies that have indicated that it’s not impossible to produce an antibody response to SARS-CoV-2, and that response will typically include antibodies that neutralize the virus. Further research will now be needed to see, among other things, how long the immunity can last.

“There is potential for further investigation of the Ad5 vectored COVID-19 vaccine for the control of the COVID-19 outbreak. An ongoing phase 2 trial in China will provide more information on the safety and immunogenicity of the Ad5 vectored COVID-19 vaccine,” the study reads

The study was published in the journal The Lancet.