The Pfizer-BioNTech Covid-19 vaccine loses some potency against the coronavirus variant that first appeared in South Africa, researchers reported Wednesday, based on lab experiments.
What the findings mean for how well the vaccine will protect real people from the variant, called B.1.351, is hard to tell. But clinical data from three other vaccines — those from AstraZeneca, Novavax, and Johnson & Johnson — have already shown the shots are not as powerful at blocking symptomatic Covid-19 cases caused by B.1.351 as by other forms of the virus.
In the new study, which was published Wednesday in the New England Journal of Medicine, researchers from Pfizer, BioNTech, and the University of Texas Medical Branch examined how well blood taken from people who had received the companies’ shot fought off a virus engineered to have the key mutations found in B.1.351. They reported that there was about a two-thirds drop in neutralization power against the variant compared to other forms of the SARS-CoV-2 coronavirus.
It can be difficult to extrapolate what such lab experiments mean for what happens if someone who received the vaccine is exposed to the variant. For one, these experiments only look at how one arm of the immune system, called neutralizing antibodies, responds to the modified virus. The vaccines generate a range of immune fighters, including other types of antibodies and T cells, so it’s possible that overall people retain more of their defenses in fending off the virus. It’s also possible that even though neutralizing antibodies don’t work as well against the variant, they can still mount enough activity to have an impact.
Moreover, vaccines that are less effective against B.1.351 or other variants that may emerge may still protect people from getting severe Covid-19; it’s just that they’re not as powerful against milder disease.
But based on the available data, some experts fear that the immunity elicited by vaccines won’t last as long against B.1.351 as against other variants, and that the immunizations won’t be able to drag down transmission of B.1.351 as well as they appear to be limiting the spread of other variants.
Already, vaccine makers are working on booster shots specifically targeting B.1.351 or that could defend against multiple strains of the coronavirus, and regulators are considering how the updated shots could be authorized without needing to go through the full gamut of clinical trials.
In a statement, Pfizer and BioNTech noted that “there is no clinical evidence to date” that their vaccine doesn’t work as well against B.1.351. “Nevertheless, Pfizer and BioNTech are taking the necessary steps, making the right investments, and engaging in the appropriate conversations with regulators to be in a position to develop and seek authorization for an updated mRNA vaccine or booster once a strain that significantly reduces the protection from the vaccine is identified.”
Moderna, the maker of the other Covid-19 vaccine authorized in the United States, last month reported that its vaccine was also less potent against B.1.351 in lab experiments, but said it believed the levels of antibodies generated should still be protective.
Both the Moderna and Pfizer-BioNTech vaccines finished clinical trials before the emergence of B.1.351 and other variants of concern, so there are no clinical data for how they defend against the newer iterations of the virus. But in their trials, both were shown to be greater than 90% efficacious at preventing symptomatic Covid-19, so some experts have argued that even if they lose some of their oomph against particular variants, they have enough cushion to remain highly protective. But the drops in efficacy in the Novavax and J&J trials against the variant have led some experts to believe that the Moderna and Pfizer-BioNTech vaccines would show similar declines if they were tested against B.1.351 in clinical settings.
Earlier this month, South Africa halted the rollout of the AstraZeneca vaccine after an analysis showed it only “provided minimal protection” against mild Covid-19, though the data were based on a small number of patients and researchers are still investigating.