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Infectious Diseases

Updated 29 May 2020

Human trial of a coronavirus vaccine shows safe and promising results

A coronavirus vaccine candidate in its phase 1 clinical trial shows promising results, according to new research.

Over the last few months, we’ve been inundated with news about research and vaccine development as various expert teams are rushing towards finding a successful vaccine against the new coronavirus.

While waiting for a vaccine or any other effective treatment, many parts of the world are relying on so-called “new norms” of physical distancing and lockdown measures.

Meanwhile, the first coronavirus vaccine to reach phase 1 clinical trial has been found to be safe, well-tolerated and able to generate an immune response against SARS-Cov-2 in humans, according to a news release.

This research was published in The Lancet.

Who developed this vaccine?

This new Ad5-NCov vaccine, an adenovirus type-5 vaccine which expresses the spike glycoprotein of the SARS-Cov-2 virus, was developed by the Beijing Institute of Biotechnology and CanSino Biologics in Tianjin, China.

The developers cloned a spike gene based on the SARS-CoV-2 virus.

Promising results

This trial was conducted among 108 healthy adults between the ages of 18 and 60 in an open-label way – this means that both the trial candidate and the research knew exactly what the candidate would be receiving. These adults showed promising results after 28 days, but the results need to be evaluated for a period of six months.

The researchers tested the blood of the candidates at regular intervals to see how the immune system was affected.

The vaccine was generally well-tolerated at all doses, with no serious adverse reactions reported.

The vaccine stimulated a rapid T-cell response in the majority of volunteers, which was greater in those given the higher and middle doses of vaccine, with levels peaking at 14 days after vaccination, according to the news release.

The researchers, however, did note that the antibody and T-cell response could be reduced by certain factors, such as pre-existing immunity to adenovirus type 5 (usually the vector or carrier of a common cold): "Our study found that pre-existing Ad5 immunity could slow down the rapid immune responses to SARS-CoV-2 and also lower the peaking level of the responses.

"Moreover, high pre-existing Ad5 immunity may also have a negative impact on the persistence of the vaccine-elicited immune responses," stated Professor Feng-Cai Zhu from Jiangsu Provincial Center for Disease Control and Prevention in China who led the study.

Mild adverse reactions

According to the researchers, the most common adverse reactions were mild pain at the injection site, slight fatigue, headache and muscle pain. Only one participant who received the highest vaccine dose experienced severe fatigue, shortness of breath and muscle pain, but these symptoms cleared up in less than 48 hours.

Limitations and next steps

According to the news release, the phase 2 trial will be randomised, double-sided and placebo-controlled to see whether the results of phase 1 could be replicated. The next stage of the trial will include 500 healthy adults, of whom 125 will be given a placebo. This phase will now also include candidates older than 60, as this age group is a key target population.

The researchers did note that the phase 1 trial had limitations due to small sample size, short duration and lack of randomised control group to identify rarer side effects, but the initial response was promising.

Further research will be needed before the vaccine becomes available.

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