The World Health Organization has welcomed an announcement by Pfizer and its German partner BioNTech that an experimental COVID-19 vaccine is more than 90 percent effective based on initial trial results.

WHO however noted that there are 10 potential vaccines in the final phase from a pool of 47 that have already had human trials conducted.

"Pfizer, BioNTech news is encouraging and we hope for good final results. But it will take time before enough people are vaccinated and we can put a dent in the COVID-19 pandemic. We must use the public health tools we have now, to protect ourselves and others," said WHO on Tuesday.

The health agency called for clinical trials to continue in order to ensure any vaccine that is developed is safe for human use and is availed affordably.

"COVID-19 cannot be beaten one country at a time," it said.

The latest development comes as the number of COVID-19 injections globally has surpassed the 50.91 million mark, with a death toll exceeding 1.26 million.

Various world leaders have also welcomed the announcement by Pfizer and its German partner BioNTech, but reiterated calls for adherence to laid out COVID-19 protocols in order to curb further spread of the virus before any vaccine is rolled out.