America is hitting its vaccination ceiling

Beyond that, the U.S. is simply fighting an uphill battle as vaccine attitudes continue to track with political sentiment. Moore pointed to a dearth of celebrities encouraging the vaccine, likely because they worry about the fallout.

Topol pointed to two additional groups: those who'd get a vaccine if mandated by their employer and those who say they've held back on getting a vaccine while it's still under emergency use authorization.

In both cases, full approval of the COVID-19 vaccine by the FDA would move things along. Schools, businesses and even the military have been reluctant to mandate shots under an EUA, even though the federal government has said it is allowed.

The gap between an EUA and full authorization is a "distinction without a difference," Moore said, but some people who don't understand the process may feel more comfortable with full authorization.