In recent months, as the global COVID-19 pandemic rages on, new variants of SARS-CoV-2 have sparked concerns about whether existing vaccines will perform as well against the evolving virus as they did in clinical trials. Three preprints posted on bioRxiv on January 19 shed some light on this question, finding that serum from vaccinated people was able to neutralize a virus with some of the same mutations as one now-widespread variant, B.1.1.7, but was less effective in neutralizing strains mimicking another variant known as 501Y.V2.

One study investigated the effects of the 501Y.V2 variant that emerged in South Africa, using serum samples from 44 people who had had COVID-19. When these sera were exposed to the variant, which has multiple mutations in its spike protein, 48 percent were unable to neutralize the virus.

“The data do raise the possibility that the protection gained from past infection with COVID-19 may be lower for re-infection with the South African variant,” Liam Smeeth, an epidemiologist at the London School of Hygiene and Tropical Medicine who was not involved in the study, tells Reuters. “The data also suggest that the existing vaccines could be less effective against the South African variant.”

In another study, serum samples from 16 people who had received the Pfizer vaccine were exposed to a virus with 10 mutations found in the spike protein of B.1.1.7, often called the UK variant. The synthesized pseudovirus was easily neutralized by antibodies in the samples, keeping hopes about vaccine efficacy high for this variant.

The third study used serum samples from 20 people who had received either the Moderna or Pfizer/BioNTech vaccine to explore how vaccine-induced immunity stood up to specific mutations that affect the spike protein. Although antibodies against SARS-CoV-2 wane as time goes on following infection, B cells retain the ability to target spike proteins and receptor binding domains which is part of the spike that allows the virus to attach to cells for infection. The efficacy of the serum was diminished against the pseudoviruses carrying the mutations compared with those with the dominant SARS-CoV-2 spike protein, and the samples neutralized the viral threat with a one- to threefold increase in antibodies. However, the small pool of samples lacks diversity in age and race, which are two crucial factors in COVID-19 outcomes, Drew Weissman, an infectious disease expert who worked on vaccine development, tells the Associated Press.

According to biologist James Naismith of Oxford University, who was not involved in the study, neutralization isn’t the only marker to measure a successful immune response.

“The real world human immune response is more than serum-based neutralisation,” Naismith tells The Guardian. “Of course we would rather neutralisation had occurred but this does not mean that the new virus will infect, make ill and spread from those who have already been infected with the original strain.”

Although the data do suggest that the vaccines might not confer the same level of protection as has been seen in clinical trials, they are still highly effective, immunologist E. John Wherry of the University of Pennsylvania who was not involved in the research explains to the Associated Press. “We don’t want people thinking that the current vaccine is already outdated. That’s absolutely not true,” he explains. “There’s still immunity here . . . a good level of protection.” 

Still, vaccinologist Gregory Poland of the Mayo Clinic who was not part of the studies, tells the AP that relying solely on vaccines to curb the spread of COVID-19 is a fool’s errand and that more needs to be done at the most basic level, like socially distancing and wearing masks. “We are shooting ourselves in the foot by allowing unmitigated transmission of this virus,” he says. 

Correction (January 22): A previous version of the article misstated that the individuals in the first study mentioned had been vaccinated, as well as the nature of the variant used in testing. We also moved Drew Weissman’s quote to be adjacent to the study he was commenting on. The Scientist regrets the errors.