The pandemic is a relentless race against Mother Nature. Waves of infection took millions of lives, and only highly effective vaccines prevented even more deaths. Now, the coronavirus is speeding up once again, mutating, evading immunity and still on the march. The arrival of subvariant BA.5 should be a reminder that the finish line in this race is nowhere to be seen.
What’s BA.5? This is the latest subvariant of omicron, which stormed the planet late last year and caused a huge wave of infection. As of now, BA.5 and a closely related variant, BA.4, account for about 70 percent of all infections in the United States, according to estimates by the Centers for Disease Control and Prevention, based in part on modeling. These two newcomers are easing out an earlier variant, BA.2.
The obscure names should not hide the punch of BA.5. Eric Topol, professor of molecular medicine at Scripps Research, says that BA.5 “is the worst version of the virus that we’ve seen.” He adds, “It takes immune escape, already extensive, to the next level, and, as a function of that, enhanced transmissibility,” well beyond earlier versions of omicron. There has not been a marked increase in hospitalizations and deaths, he reports, because there is so much immunity built up from the winter omicron wave. But there are aspects of this new variant very much worth keeping an eye on as the United States remains stuck at an uncomfortably high plateau of pandemic misery. And the new variants are driving a case surge in Europe.
counterpointBA.5 should not change how Americans think about living with covid
At the core of the BA.5 difference is its biology. Evolution has given it more fitness, a term that incorporates its ability to transmit, grow and evade immunity; the variant shows “marked difference from all prior variants,” reports Dr. Topol. One way it does so is by evading the body’s immune system, and BA.4 and BA.5 together are “the most immune-evasive variants” seen in multiple studies to date.
Whether BA.5 will lead to more severe disease isn’t clear yet. But knowing that the virus is spreading should reinforce the need for the familiar mitigation measures: high-quality face masks, better air filtration and ventilation, and avoiding exposure in crowded indoor spaces.
An important question is whether the next boosters should include the new variants. Does a booster with an earlier version of the virus make any sense if that variant has disappeared from the population? The Food and Drug Administration has recommended manufacturers build a bivalent or two-component vaccine, with old and new variants as the target. It certainly makes sense to be flexible — as Wayne Gretzky put it, to skate where the puck is going, not where it has been. But time is short, and who knows what variants will be present later this year? In the longer term, variant chasing is hardly ideal. The greatest need is for next-generation vaccines that are more broadly protective, more durable (with longer-lasting immunity) and that can dampen transmission. There is a major research effort underway to achieve this, but the finish line is not yet in sight.