German biotech firm BioNTech and U.S. drugmaker Pfizer on Monday reported additional data from their experimental COVID-19 vaccine that showed it was safe and induced an immune response in patients.
BioNtech's U.S. shares gained 12%, while Pfizer's stock rose 3.6% in early trading.
The companies said the data also demonstrated an induction of high level of T-cell responses against the novel coronavirus.
More than 150 possible vaccines are being developed and tested around the world to try to stop the pandemic. There are 23 candidates in human clinical trials, including from Moderna and AstraZeneca.
Experts have cautioned a safe and effective vaccine will take 12-18 months to develop.
The results were disclosed from a trial in Germany testing 60 healthy volunteers, and come after the companies earlier this month reported data from a corresponding early-stage trial in the United States.
The trial showed that volunteers given two doses of the vaccine produced virus-neutralizing antibodies, similar to the U.S. trial.
The data is available on an online preprint server at medrxiv and is undergoing scientific peer-review for potential publication, the companies said.