This fall, millions of Americans might be lining up for yet another kind of COVID vaccine: their first-ever dose that lacks the strain that ignited the pandemic more than three and a half years ago. Unlike the current, bivalent vaccine, which guards against two variants at once, the next one could, like the first version of the shot, have only one main ingredient—the spike protein of the XBB.1 lineage of the Omicron variant, the globe’s current dominant clade.
That plan isn’t yet set. The FDA still has to convene a panel of experts, then is expected to make a final call on autumn’s recipe next month. But several experts told me they hope the agency follows the recent recommendation of a World Health Organization advisory group and focuses the next vaccine only on the strains now circulating.
The switch in strategy—from two variants to one, from original SARS-CoV-2 plus Omicron to XBB.1 alone—would be momentous but wise, experts told me, reflecting the world’s updated understanding of the virus’s evolution and the immune system’s quirks. “It just makes a lot of sense,” said Melanie Ott, the director of the Gladstone Institute of Virology, in San Francisco. XBB.1 is the main coronavirus group circulating today; neither the original variant nor BA.5, the two coronavirus flavors in the bivalent shot, is meaningfully around anymore. And an XBB.1-focused vaccine may give the global population a particularly good shot at broadening immunity.
At the same time, COVID vaccines are still in a sort of beta-testing stage. In the past three-plus years, the virus has spawned countless iterations, many of which have been extremely good at outsmarting us; we humans, meanwhile, are only on our third-ish attempt at designing a vaccine that can keep pace with the pathogen’s evolutionary sprints. And we’re very much still learning about the coronavirus’s capacity for flexibility and change, says Rafi Ahmed, an immunologist at Emory University. By now,…
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