In the study conducted in Germany on 60 healthy volunteers, the vaccine induced virus-neutralizing antibodies in those given two doses, in-line with previous results from an early-stage US trial.

BioNtech's US shares rose 5%, while Pfizer's stock was marginally higher at $36.44.

Under expedited development plans, the companies have said they expect to begin a trial later this month with up to 30,000 subjects with the aim of demonstrating the vaccine's efficacy.

A safe and effective vaccine against the novel coronavirus is seen as essential to ending a pandemic that is still raging and has claimed more than 600,000 lives worldwide.

In the German study, the vaccine also generated a high level of T cell responses against the coronavirus. T cells, a type of white blood cell, are an important component of the immune system's attack against foreign invaders, such as viruses.

"Today's data includes the first evidence of the vaccine generating a T-cell response, which could be critical in order for patients to develop durable immunity to the novel coronavirus," said Mizuho analyst Vamil Divan.

Trial subjects experienced no serious side-effects from the vaccine, though some reported flu-like symptoms and injection site reactions.

The results come as separate results were released for two other experimental COVID-19 vaccines on Monday.

AstraZeneca's vaccine being developed with Oxford University researchers appeared to be safe and produced an immune response in early-stage clinical trials. Another vaccine being developed by CanSino Biologics Inc and China's military research unit also appeared to be safe and induced immune responses in most recipients.

More than 150 potential coronavirus vaccines are in various stages of development around the world, with 23 candidates already being tested in people, according to the World Health Organization.

Separately on Monday, Britain signed deals to secure 30 million doses of the Pfizer/BioNTech vaccine, as well for additional doses from French group Valneva.