New research suggests that Pfizer’s Covid-19 vaccine can protect against a mutation found in two highly contagious variants of the coronavirus that erupted in Britain and South Africa.

Those variants are causing global concern. They both share a common mutation called N501Y, a slight alteration on one spot of the spike protein that coats the virus. That change is believed to be the reason they can spread so easily.

The study, which was done by Pfizer and scientists from the University of Texas Medical Branch is preliminary and has not yet been reviewed by experts, according to media reports, a key step for medical research.

But "it was a very reassuring finding that at least this mutation, which was one of the ones people are most concerned about, does not seem to be a problem” for the vaccine, said Pfizer chief scientific officer Dr. Philip Dormitzer.

The study was conducted on blood taken from people who had been given the vaccine.

Viruses constantly undergo minor changes as they spread from person to person. Scientists have used these slight modifications to track how the coronavirus has moved around the globe since it was first detected in China about a year ago. 

British scientists have said the variant found in the U.K. – which has become the dominant type in parts of England -- still seemed to be vulnerable to vaccines. That mutant has now been found in the U.S. and numerous other countries.

But the variant first discovered in South Africa has an additional mutation that has scientists on edge, one named E484K. 

The Pfizer study found that the vaccine appeared to work against 15 additional possible virus mutations, but E484K wasn’t among those tested. Dormitzer said it is next on the list.