Are vaccines variant-proof ? Here’s some good news
SCIENCE has delivered some incredible achievements in the fight against COVID-19, not least of which is the swift development of several highly effective vaccines. The question is, will the shots continue to offer strong protection even as the SARSCoV-2 virus mutates and evolves?
We’ve already seen virus variants sprout up, from B.1.1.7 in the UK to B.1.351 in South Africa and P.1 in Brazil. Now we have B.1.617 in India and two variants — B.1.429 and B.1.232 — in California. Some of these variants have been found to be more contagious and potentially deadlier than the original strain, and more variants are sure to arise in any country or region where the virus is left to multiply and infect people at a high rate. Even in places where the virus seems to be under control, variants are a worry. In Israel, there have been reports of “breakthrough” infections among vaccinated people, mostly of the B.1.351 variant. These are big concerns. But there are hopeful signs that vaccine science is staying ahead of the variants in the most important ways.
First, some good news regarding potential “booster” shots. A recent study found that a new vaccine targeting the “spike protein” — the rod-like structure on the surface of the virus — of the South African variant induced a strong immune response in nonhuman primates that had been previously vaccinated against the older virus strain. Moderna, Inc. has also noted, though not published data, that its new mRNA-1273.351 vaccine was able to boost the immune response of previously vaccinated animals to provide increased activity against the B.1.351 variant.
These two studies address a key concern I had around the risk of “original antigenic sin” — that is, that a new vaccine against a slightly different virus variant might induce an immune reaction against the original version of the virus rather than the variant it was targeting. While we need to see data from a human study, which Moderna could have sometime in the second quarter, these results suggest we are one step closer to having a variant vaccine, should we need one.
As for existing vaccines, promising new data suggests that the shot now in use from Pfizer, Inc. and BioNTech SE is effective in protecting against variants. Results from a small South African trial of the Pfizer-BioNTech vaccine showed 100% efficacy against the B.1.351 variant. Though based on only a few cases, it showed that none of those who were vaccinated as part of the trial tested positive, compared with nine who contracted the virus while taking a placebo (six of whom contracted the South African variant). It’s possible that the vaccinated group didn’t encounter the virus and a lot more cases are needed to draw a firm conclusion, but this early data suggests the efficacy against this variant is robust. This may explain why Pfizer and BioNTech have decided to use their original vaccine as a third booster, if it proves necessary, and not develop a shot using the spike protein from the B.1.351 variant.
But what about that news from Israel about breakthrough infections? In a nutshell, I am not that worried about it. We already knew that the vaccines can’t stop all infections. We also knew from several studies by different groups that the B.1.351 variant is not as susceptible to the antibodies generated by the PfizerBioNTech or Moderna vaccines as the ancestral versions of the virus are. So infections in vaccinated people in areas where the variant is circulating would be more likely to be by the B.1.351 variant than not. But while people may get infected by variants despite being vaccinated, the critical point is whether they develop anything but mild symptoms. What we truly care about is severe COVID-19 disease and hospitalizations. If all the infected individuals had only mild symptoms, or none at all, then that actually proves the point: The vaccine is doing its job in preventing severe disease and hospitalizations. This appears to be the case.
I am not suggesting that we stop worrying about variants. As I have written before, there needs to be much more genomic sequencing across the world to ensure we are on top of any changes in the virus. But we need not panic. Variants occur when the virus is multiplying at high levels. Having a fully vaccinated population significantly reduces its chances of doing that. What we do need to do is to get vaccines faster to the nations that cannot afford them.