A UK vaccine against coronavirus has shown promising results, findings of the first phases of the study suggest.

The early-stage trial showed the vaccine is safe, causes few side effects, and induces strong immune responses, results published in The Lancet said.

However, scientists warned it is still too soon to know if the results are enough, and larger trials are currently under way.

The vaccine, developed by the University of Oxford, is called ChAdOx1 nCoV-19 and is delivered via a chimpanzee virus, called the vaccine vector.

It is made from a genetically engineered virus that causes the common cold in chimpanzees, which is then engineered to express the coronavirus spike protein to trigger a strong immune response in the human body.

The UK government has already ordered 100 million doses of the vaccine.

Trials involving 1,077 healthy adults between April 23 and May 21 showed the injection led to them making antibodies and white blood cells that can fight COVID-19. It did not produce any serious side effects.

Professor Sarah Gilbert, from the University of Oxford, UK, said: There is still much work to be done before we can confirm if our vaccine will help manage the COVID-19 pandemic, but these early results hold promise.

As well as continuing to test our vaccine in phase-three trials, we need to learn more about the virus for example, we still do not know how strong an immune response we need to provoke to effectively protect against Sars-Cov-2 infection.

If our vaccine is effective, it is a promising option as these types of vaccine can be manufactured at large scale.

A successful vaccine against Sars-Cov-2 could be used to prevent infection, disease and death in the whole population, with high-risk populations such as hospital workers and older adults prioritized to receive vaccination.

Scientists behind the trial said the current trial is too preliminary to confirm whether the new vaccine effectively protects against coronavirus.

An ideal vaccine should be effective after one or two vaccinations, work in target populations including older people and those with preexisting health conditions, offer protection for a minimum of six months, and reduce transmission of the virus to contacts.

Phase 3 trials for the vaccine are now underway in Brazil, South Africa, while combined phase 2/3 trials are continuing in the UK.