The vaccine race against the coronavirus variants, explained

The world is now locked in an arms race with Covid-19, as multiple effective vaccines are being deployed (at staggeringly different rates) around the world. At the same time, new variants of the SARS-CoV-2 virus have been rapidly spreading.

The Covid-19 vaccines that are being distributed in the US, as well as the newly authorized Johnson & Johnson vaccine, have been shown to almost eliminate deaths and hospitalizations from the disease, even for people infected with the new mutations. For a disease that has infected more than 114 million people around the world in just over a year, this is tremendously good news.

But it’s no time to kick back.

There’s evidence that the virus is evolving in ways that can reduce the effectiveness of Covid-19 vaccines — particularly when they’re up against the variant discovered in South Africa. Both Johnson & Johnson and Novavax’s vaccine efficacy rate dropped in the South Africa arm of their clinical trials (from 72 in the US to 64 percent in South Africa and from 89 in the UK to 49 percent, respectively).

The vaccines still worked against their new foe in the majority of trial participants. The human immune response, after all, is robust and multi-layered. It can adapt to different versions of the virus that come along, which is why vaccine-induced immunity is unlikely to “fall off a cliff and go from 95 percent to zero,” as University of Utah evolutionary virologist Stephen Goldstein told Vox.

However, the situation is still dicey. “Eventually, when the majority of the susceptible population is vaccinated with effective vaccines, the variant better suited for survival in the new host will be one that has the ability to evade the vaccine-induced immunity,” researchers warned in a March 1 letter published in Nature. Such a variant could “decrease, and even abolish, the beneficial effects of a broad immunization program.”