Newly emerging, fast-spreading variants of the coronavirus might reduce the protective effects of two leading vaccines.

Michel Nussenzweig at the Rockefeller University in New York City and his colleagues analyzed blood from 20 volunteers who received two doses of either the vaccine developed by Moderna or that developed by Pfizer–BioNTech (Z. Wang et al. dn; 2021). 

Both vaccines carry RNA instructions that prompt human cells to make the spike protein that the virus uses to infect cells. This causes the body to generate immune molecules called antibodies that recognize the spike protein. Three to 14 weeks after the second jab, the study participants developed several types of antibody, including some that can block SARS-CoV-2 from infecting cells. Some of these neutralizing antibodies were as effective against viruses carrying certain mutations in the spike protein as they were against widespread forms of the virus. But some were only one-third as effective at blocking the mutated variants.

Some of the mutations that the team tested have been seen in coronavirus variants that were first identified in the United Kingdom, Brazil and South Africa; at least one of these variants is more easily transmitted than other forms of the virus now in wide circulation.The findings suggest that vaccine-resistant variants might emerge, meaning that COVID-19 vaccines could need an update. They have not yet been peer reviewed.

Neutralizing antibodies against SARS-CoV-2 block particles of the virus, which makes them some of the body’s most potent weapons against the new pathogen. Most of the neutralizing antibodies that researchers have studied target a region of the virus’s spike protein called the receptor-binding domain (RBD). But previous studies have also identified neutralizing antibodies that act against other portions of spike — particularly a region called the N-terminal domain (NTD).

 David Veesler at the University of Washington in Seattle and his colleagues analysed the blood of people who had recovered from COVID-19, and identified 41 antibodies that recognize the NTD (M. McCallum et al. Preprint at bioRxiv https://doi.org/fq92; 2021). Some proved to be as potent at blocking infection as were antibodies that recognize the RBD. Hamsters treated with one of the strongest NTD-targeting antibodies were protected from SARS-CoV-2 infection. Worryingly, the authors found that variants of the coronavirus first identified in the United Kingdom and South Africa carry mutations that might weaken the effects of some NTD antibodies. The findings have not yet been peer reviewed.