The coronavirus is a moving target, and both vaccines and vaccine protocols will almost certainly need to shift along with it. But some experts worry that the debate over dosing strategies will undercut public trust in the vaccines themselves. “We went through all these very carefully controlled clinical trials, and at the end, you’re like, ‘Oh, just change it up’?” says Gigi Gronvall, an immunologist at the Johns Hopkins Center for Health Security. From an optics standpoint, she told me, “that doesn’t seem like a good idea.”
Those who have already made up their minds about vaccinating or not vaccinating might not be affected by these uncertainties. But people who are still unsure—the “movable middle”—might balk at the notion of scientists operating on guesswork, says Alison Buttenheim, a behavioral scientist who studies vaccine acceptance at the University of Pennsylvania. “For a decision that for some people is already pretty fraught, it just increases the chances that they’ll just throw up their hands and say, ‘Forget it.’” When the experts bicker, what sticks in people’s minds might be the arguing, rather than the merits of the arguments themselves.
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Hewlett told me he’s worried that vaccine hesitancy could exacerbate disparities in Black and Latino communities, which have already been disproportionately hurt by the pandemic and where structural racism in medicine has seeded decades of distrust. “People think, Maybe I should wait until they’ve sorted it all out before I move forward,” he said. He’s already hearing the refrain of “wait and see” from some of his patients and colleagues.
The evidence for delaying people’s second dose might be accumulating, but the strategy will still need to overcome behavioral biases to succeed. Multi-shot vaccines are hard to give, especially in regions of the world in which people do not have consistent access to medical resources. A wider dosing interval increases the likelihood that people will forget about or lose interest in returning, says Wood, the marketing researcher. Distant deadlines are a great excuse to procrastinate, until the task itself seems wholly unimportant.
A prescribed three- or four-week gap is easier to adhere to. “If we leave it open-ended, it’s an architecture-free choice, and it’s just much less likely to happen,” Buttenheim says. “We don’t want you deciding when your second dose should be.”
Vaccine regimens aren’t set in stone, even after they’re formally FDA-approved (which none of the coronavirus vaccines are, yet, only authorized for emergency use). The HPV vaccine, which was initially delivered in three doses, is now doled out in two to certain age groups. Other vaccines have been rolled into multifunctional formulas that protect against multiple bugs at once. The country might soon hit a point when the rollout rules need to change. But even when such shifts are supported by a multitude of data, implementation requires communicating them to the public, and that’s never easy—especially if trust in the vaccine is already fractured.