COVID vaccines, like most others, are best at staving off severe disease and death; against BA.5 and its kin, especially, that protection is likely to be durable and strong. But those same shields will be far more flimsy and ephemeral against milder cases or transmission, and can only modestly cut down the risk of long COVID. And when partnered with a compromised or elderly immune system, the shots have that much less immunological oomph. Then say a new immunity-dodging variant appears: The shots could lose even more of their strength.
Vaccine performance also depends on how and how often the shots are used. The more people take the doses, the better they will work. But no matter how hard we try, this reformulated shot “is not going to cover everyone, either because they choose not to get it or won’t be able to access it,” says Katia Bruxvoort, an epidemiologist at the University of Alabama at Birmingham. People who haven’t yet finished their primary series of COVID shots aren’t expected to be able to sign up for the BA.5 boosts—a policy that Bhattacharya thinks is a big mistake, not least because it will disadvantage anyone who seeks a first brush with vaccine protection this fall. “The better the degree of breadth right at the beginning,” he told me, the better future encounters with the virus should go. Most kids under 12 remain in that totally unvaccinated category; even those who have completed their initial round of shots won’t be eligible for the revamped recipe, at least not in this first autumn push. Among people who can immediately get the new booster, uptake will probably be meager and unbalanced. “Realistically, the boosters are going to be concentrated in the places that have been the least impacted by the pandemic” and in people who have already had at least one boost, says Anne Sosin, a public-health researcher at Dartmouth. Such widening gaps in protection will continue to offer the virus vulnerable pockets to invade.
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