More than 80% of Americans 65 and older have received at least one dose of a coronavirus vaccine, per the CDC, but millions across the country remain unvaccinated — particularly in the South.

Why it matters: Seniors who have yet to receive their shot remain highly vulnerable to the virus even as the country overall becomes safer.

By the numbers: More than two-thirds of residents 65 and older have received at least one dose of the vaccine in every state. But some states are much closer than others to universal vaccination among seniors.

• States in the Northeast, including Vermont, Rhode Island and Massachusetts, have the highest vaccination rates among seniors.
• Southern states — like Alabama, Mississippi and Tennessee — have some of the lowest.

Yes, but: Some states have done a worse job vaccinating seniors than their overall populations, and a state's political leaning isn't necessarily an indicator of how many seniors have gotten their shots.

• Hawaii, for example, is the state with the lowest vaccination rate among seniors — only 69.3% have received at least one dose. But 39.8% of all state residents have received at least one dose, which is nearly equivalent to the national average.
• Ruby-red South Dakota is among states with high senior vaccination rates, mirroring its above-average vaccination rate in the general population as well.

Between the lines: It's unclear whether the remaining 20% of people 65 and older are struggling to get access to a vaccine, or simply don't want one.

• KFF polling has found that only 8% of seniors say they definitely don't want to get a vaccine, and 1% say they'll only get one if required. Another 7% said they want to "wait and see" before getting a shot.
• Put together, that's 16% of seniors, which suggests that it'll be an uphill battle to get shots in the arms of many seniors who remain unvaccinated.