The first Covid-19 vaccine to be tested in humans has been found to be safe, well-tolerated, and able to generate an immune response against the virus, according to new research published in The Lancet.

The Phase 1 trial, involving 108 healthy adults aged 18 to 60, showed promising results after 28 days, but final results will be evaluated in six months.

Further trials will also be needed to determine whether the immune response triggered by the vaccine effectively protects against the SARS-CoV-2 infection which causes Covid.

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"These results represent an important milestone," Professor Wei Chen, from the Beijing Institute of Biotechnology in China, who is responsible for the study.

However, he stressed that the 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.

"This result shows a promising vision for the development of Covid-19 vaccines, but we are still a long way from this vaccine being available to all.”

The creation of an effective vaccine is seen as vital to beating the pandemic.

Currently, there are more than 100 candidate Covid-19 vaccines in development worldwide.

The vaccine being trialled in China uses a de-activated adenovirus - one of the causes of the common cold - as a conduit to deliver genetic material to the cells that codes for SARS-CoV-2.

These cells then produce the virus' distinctive spike protein, and travel to the lymph nodes where the immune system creates antibodies that will be able to recognise that spike protein and fight off the coronavirus.

Volunteers were enrolled from one site in Wuhan, China, and assigned to receive either low, medium or high doses of the vaccine.

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The researchers tested the volunteers’ blood at regular intervals following vaccination to see whether the vaccine stimulated both antibody and T cell production - the two strands of human immune response.

It is thought that the ideal vaccine will be able to generate both antibody and T cell responses.

After 28 days, most participants had a four-fold increase in 'binding' antibodies, which that can attach to the coronavirus but do not necessarily attack it.

However, half to three-quarters of participants had developed neutralising antibodies, which do attack pathogens.

Importantly, the Ad5-nCoV vaccine also stimulated a rapid T-cell response in the majority of volunteers, which was greater in those given the higher and middle doses of vaccine.

T-cells are important because they are capable of recognising and destroying other cells in the body infected with the virus – not just the viral pathogen itself.

Further analyses showed that 28 days after vaccination, the majority of recipients showed either a positive T-cell response or had detectable neutralising antibodies.

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However, the authors note that both the antibody and T-cell response could be reduced by high pre-existing immunity to adenovirus type 5.

A randomised, double-blinded, placebo-controlled Phase 2 trial of the Ad5-nCoV vaccine has now been initiated in Wuhan to determine whether the results can be replicated, and if there are any adverse events up to six months after vaccination.

It will involve 500 participants being given different doses of the vaccine or a placebo vaccine.