A mutation found in fast-spreading coronavirus variants does not negate the Covid-19 vaccine from Pfizer and BioNTech, researchers reported late Thursday.
The result is positive, if expected, evidence that existing vaccines will be able to withstand some mutations to the SARS-CoV-2 coronavirus without losing efficacy. But experts noted that this vaccine and others will still need to be tested against other mutations of concern, and that the new study only looked at one key mutation contained in the variants, not the full variants.
“We’re working on that part now” in additional studies, Philip Dormitzer, Pfizer’s vice president and chief scientific officer of viral vaccines, told STAT.
In the study, scientists engineered a version of the virus to include the mutation called N501Y. The mutation is found in variants that seem to transmit faster than other forms of the virus, including one first identified in the United Kingdom that is now spreading in other countries, including the United States.
The scientists then compared how well blood taken from 20 people who had received the vaccine fended off the mutated form of the virus versus an earlier form. Their finding: there was “no reduction in neutralization activity against the virus” with the mutation, they wrote.
The study, conducted by scientists at Pfizer and the University of Texas Medical Branch, was posted to a preprint server, meaning it has not been peer-reviewed.
The concern is that mutations in particular spots in the RNA genome of the virus could change the appearance of certain areas on the virus, making them less recognizable to antibodies elicited by the vaccines.
In this case, N501Y leads to a change on a key part of the virus’ spike protein, which helps the virus attach to human cells and establish an infection. Portions of the spike protein are prime target sites for antibodies.
“These data don’t suggest a need for a change, but the mutations are hitting close enough to home that we need to be prepared,” Dormitzer said.
N501Y seems to help the coronavirus attach to the receptor ACE2 on cells even better than other forms of the virus, meaning people exposed to the virus are more likely to contract it. This could help explain why variants with the mutation seem to be more transmissible.
In addition to the variant first seen in the U.K., N501Y also appears in a variant identified initially in South Africa. But both the variants contain other mutations as well, so scientists need to test vaccines against the full variants to gauge whether the protection they confer is sustained. One key mutation called E484K appears to make the virus less recognizable to certain antibodies and has emerged as a particular concern. That mutation is present in the variant in South Africa, though not the version that first appeared in the U.K.
Pfizer and its collaborators are in the process of testing its vaccine against the variants. Separately, Moderna — which also has a Covid-19 vaccine authorized in the United States — has said it is conducting similar research.
Scientists had expected that the vaccines authorized now or in development wouldn’t be taken down by single mutations. For one, antibodies generated by vaccines target multiple parts of the virus, so changes at one site shouldn’t sap the immune system’s ability to recognize the pathogen. Vaccines also induce other parts of the immune system to kick into gear, including fighters called T cells.
Pfizer has now tested its vaccine against more than a dozen SARS-2 mutations without finding anything alarming, Dormitzer said.
“I don’t want to be a Pollyanna here … we have to test each one as they come, but so far so good,” he said.
If anything, a mutation might reduce how well vaccines work, not render them ineffective entirely, experts stress. But they do say it’s possible that the virus will pick up several mutations over time — perhaps years — that could threaten the protection the immunizations provide. In that case, the vaccines would have to be tweaked to match the genetic changes in the virus.
Scientists and regulators are now trying to figure out at what point they would decide such updates to the vaccines are needed.