Pfizer COVID-19 vaccine likely to work against new, rapidly-spreading variants: Study

A new study offers some reassurance that Pfizer and BionTech's COVID-19 vaccine is likely to protect patients against two new variants of the COVID-19 virus: one now circulating rapidly in U.K. and the other South Africa.

Since the emergence of these new variants, scientists have expressed confidence that currently authorized vaccines would work against them -- but cautioned that more studies were needed to be sure.

Now, in a study that has not yet been peer reviewed, researchers from Pfizer and the University of Texas Medical Branch have found that the vaccine seems to work against one of the mutations that makes the U.K. and South African variants distinct.

Both new variants -- the result of random copying errors in the virus's genetic code -- appear to be easier to transmit, but not more deadly. Working in a laboratory, researchers modified a version of the coronavirus to include a specific copying error that's believed to make the U.K. and South African variants more contagious.

They then tested that modified virus against blood samples from 20 people who volunteered for Pfizer's clinical trial and received both vaccine doses, finding that the virus-fighting antibodies were still able to "neutralize" the modified virus.

Pei-Yong Shi, Ph.D., University of Texas Medical Branch in Galveston, the lead researcher on the study, told ABC News this is "the first study to show that one of the most prominent mutations in the fast-spreading U.K. and the South African strain ... doesn't affect the neutralizing activity of the current vaccine."

Though their experiment was conducted in a laboratory, it offers promising reassurance that people who are immunized with Pfizer's vaccine will also likely be protected from the new variants in real life. Shi said some of the antibodies produced by the vaccine "may be weakened by a single mutation, but others will remain active," which he believes will continue to provide protection from the variants.

However, more research is still needed to examine the vaccine's effectiveness in the context of the unique set of mutations found in the U.K. and South African variants -- not just the select mutation researchers zeroed in on in their modified virus experiment. Shi and his colleagues are currently working on acquiring both variants to test the vaccine's efficacy in the laboratory.

And studies are ongoing to confirm that other vaccines -- including a vaccine from Moderna, authorized in the United States, and one from AstraZeneca/Oxford, authorized in the UK and India -- will also work against the new variants.

But experts say it's likely many of the vaccines available today will offer some protection against new viral variants because they elicit a multi-pronged defense inside the body's immune system.

"When you get vaccinated, the immune response that you make is called polyclonal, which means it's against many different parts of the virus," said Dr. Anthony Fauci, the nation's top infectious disease expert, during a Facebook Live event with California Gov. Gavin Newsom last week.

"Even though you have one part of the virus that's changed, it's very likely that the other components of the vaccine induced response will protect you," Fauci said.

But experts also warn the out-of-control spread of COVID-19 means more mutations and more variants are likely to emerge due to an increased likelihood of those random copying errors, which is why researchers in this study recommend speeding up vaccination of the general populace to keep the virus in check. Meanwhile, the new U.K. variant has now been detected in at least eight states within the U.S.

"There is a definite concern over the long period," epidemiologist and ABC News contributor Dr. John Brownstein told ABC News last week. "Over months and years, it could pose a problem with the vaccine … but I think in the coming six months, we'll be totally fine with the current vaccine."

Despite the fact that this vaccine is still effective against these current variants, Shi warns that after we have been vaccinated, "the virus will be evolving under different pressures" and we will need to be vigilant in our monitoring to prevent another severe outbreak.

Sean Llewellyn, M.D., Ph.D, is a family medicine resident physician at the University of Colorado and a contributor to the ABC New Medical Unit. Sony Salzman is the unit's coordinating producer.

Dr. Mishal Reja contributed to this report.