New COVID-19 Strains Not Likely to Knock Out Vaccines but Could Weaken Efficacy, Experts Say

Scientists are closely monitoring the potential impact of mutations of the SARS-CoV-2 virus on the effectiveness of COVID-19 vaccines, but for the moment the new strains don’t appear able to completely evade their protective effect.

A new, more infectious viral mutation in South Africa has raised renewed concerns following a rapidly spreading variant that was identified in the UK just before Christmas. Both have spread to the U.S. and elsewhere, increasing fears that they could sidestep vaccines just as countries around the world gear up their vaccination efforts.

Experts say the strains might reduce vaccine efficacy and they will require more study, but many believe that current vaccines will still defend against them.

“Most of us believe that the existing vaccines are likely to work to some extent to reduce infection [and] transmission rates and severe disease against both the UK and South African variants,” said Julian Tang, a consultant virologist at Leicester Royal Infirmary. “The various mutations have not altered the S protein shape that the current vaccine induced antibodies will not bind [to] at all.”

While Tang projected that two additional mutations in the South Africa variant might cause more problems for vaccine effectiveness than the UK strain, he said that the Pfizer/BioNTech, Moderna, AstraZeneca and Sputnik V vaccines can be rejiggered to improve their effectiveness against the variant in a matter of months if the impact on efficacy is severe enough.

Similarly optimistic is Francois Balloux, director of the University College London’s Genetics Institute, who expects that the South African variant will not be able to sneak past the protection given by current vaccines. He did warn, however, that new mutations that lessen efficacy could occur eventually.

“It’s possible that new variants will affect the efficacy of the COVID vaccines, but we shouldn’t make that assumption yet about the South African one,” he said.

William Hanage, associate professor of epidemiology at Harvard T.H. Chan School of Public Health, said he was “relatively sanguine” concerning the strains because of the way COVID-19 vaccine immunity functions. Because it targets many different parts of the virus’ spike protein, he predicted that even if efficacy is in fact reduced by the strains, it won’t be to a notable degree.

“At present we don’t think there is any reason to believe vaccine efficacy will be much lower against the emerging variants. The evidence base for this is better for the UK variant, but much of the same principles apply to the [South African] variant,” he said.

Though the three experts shared hope that current vaccines will work against the new strains, the South African variant has set off alarms for researchers and is being extensively studied because some of its mutations are significant, according to James Naismith, director of Oxford’s Rosalind Franklin Institute.

“Viruses mutate and new strains will emerge. The so-called South African strain has a number of changes, and scientists are working flat-out to understand their significance. Some of the changes are quite significant and thus scientists are paying a lot of attention,” he said. “We do not yet know enough to say more than this.”

Viral mutations are not uncommon, but some viruses mutate far more than others, such as influenza, whose constant changes require annual vaccine updates. In the case of SARS-CoV-2, variants have occurred since the pandemic’s start, and thousands of mutations have been seen so far, said Lawrence Young, virologist and professor of molecular oncology at Warwick Medical School.

Young said that while the UK variant isn’t likely to reduce the effectiveness of current vaccines, the South African variant has undergone more spike mutations that make it more of a potential threat to vaccine protection. He also noted that while both variants are more infectious it’s not yet known if they cause more severe disease.

Further research will be critical to understanding the new strains and mounting a response, if necessary. Monitoring must also continue for SARS-CoV-2 mutations in general, as vaccine updates might be required eventually, said Jesse Bloom, an evolutionary virologist at the Fred Hutchinson Cancer Research Center.

“I am optimistic that current vaccines will remain quite useful even against viral lineages with mutations such as [the South African one] that reduce neutralization titers,” he said, adding that “ SARS-CoV-2 mutations remain an important area for continued scientific study.” — James Miessler