As coronavirus cases rise across the country, some experts are again calling to delay the second doses of vaccines — and to target vaccines to the hardest-hit areas.

Why it matters: America's vaccination strategy should adapt to a changing pandemic, these experts argue.

What they're saying: "It's time for the Biden admin to delay 2nd vax doses to 12 weeks. Getting as many people as possible a vax dose is now urgent," tweeted Atul Gawande, who was a member of President Biden's coronavirus transition team. "I was on the fence on this. I'm not anymore."

• Part of what got him off the fence, Gawande said, is the fact that more dangerous variants are an increasing share of U.S. cases. He also pointed to a recent CDC study that found the mRNA vaccines reduced the risk of coronavirus infection by 80% after the first dose.
• A paper published yesterday in Nature argues that delaying or halving doses could slow the development of new, vaccine-resistant variants.

The other side: Opponents of delaying second doses — including the U.S. government, at least for now — note that we don't know how long immunity from just one dose lasts.

• “We don’t think it’s worth taking the chance," NIAID Director Anthony Fauci said. “We know that the level you get with a single dose, no question, is substantially lower than the level of antibody you get with a double dose. And we know that when we’re dealing with variants, you need a cushion.”

What's next: There's a separate debate brewing over whether more vaccine doses should be sent to hotspots.

• Michigan Gov. Gretchen Whitmer and New York City Councilmember Mark Levine — representatives of the two biggest hotspots in the country — have recently advocated for that approach.
• But the White House isn't inclined to change its population-based distribution formula.
• “I think we shouldn’t do that at the central level…I don’t think it’s necessary," Fauci said. "I think it can be accomplished at the local level.”