A study conducted by the Ragon Institute of MGH, MIT and Harvard and Massachusetts General Hospital, has found that neutralizing antibodies induced by the Pfizer and Moderna COVID-19 vaccines were significantly less effective against the new variants.
The study, published in Cell, examined the impact of these vaccines on new variants of the virus that arisen throughout the world.
New variants of SARS-CoV-2 have been identified in California, Denmark, the U.K., South Africa and Brazil/Japan.
Researchers used their experience measuring HIV neutralizing antibodies to create similar assays for COVID-19, comparing how well the antibodies worked against the original strain versus the new variants.
“We were able to leverage the unique high-throughput capacity that was already in place and apply it to SARS-CoV-2,” says Balazs, who is also an assistant professor of Medicine at Harvard Medical School and assistant investigator in the Department of Medicine at MGH. “When we tested these new strains against vaccine-induced neutralizing antibodies, we found that the three new strains first described in South Africa were 20-40 times more resistant to neutralization, and the two strains first described in Brazil and Japan were five to seven times more resistant, compared to the original SARS-CoV-2 virus.”
Neutralizing antibodies work by binding tightly to the virus and blocking it from entering cells. By doing so it prevents new infection. It functions like a key in a lock. This binding is impossible if the antibody’s shape and the virus’s shape are not perfectly matched to each other.
If the shape of the virus continues to change —then the antibody may no longer be able to recognize and neutralize the virus as well. The virus would then be described as resistant to neutralization.
“In particular,” says Wilfredo Garcia-Beltran, MD, Ph.D., a resident physician in the Department of Pathology at MGH and first author of the study, “we found that mutations in a specific part of the spike protein called the receptor binding domain were more likely to help the virus resist the neutralizing antibodies.” The three South African variants, which were the most resistant, all shared three mutations in the receptor binding domain. This may contribute to their high resistance to neutralizing antibodies.
Currently, all approved COVID-19 vaccines work by teaching the body to produce an immune response, including antibodies, against the SARS-CoV-2 spike protein. While the ability of these variants to resist neutralizing antibodies is concerning, it doesn’t mean the vaccines won’t be effective.
“The body has other methods of immune protection besides antibodies,” says Balazs. “Our findings don’t necessarily mean that vaccines won’t prevent COVID, only that the antibody portion of the immune response may have trouble recognizing some of these new variants.”