​​The percentage of adults vaccinated against COVID-19 who have gotten their booster more than doubled in November in a “significant uptake,” a Kaiser Family Foundation (KFF) poll found, as the U.S. expanded eligibility to the extra dose.

The KFF Vaccine Monitor for November released Thursday found 23 percent of vaccinated adults said they have had their booster shot, compared to 10 percent who said the same in October.

While a majority of the vaccinated adults — 56 percent — said they are likely to get their booster once eligible, 18 percent said they will probably or definitely not get a booster dose.

Little change among unvaccinated: Meanwhile, the poll found no “significant” progress in the percentage of vaccinated adults since September, with 73 percent saying they have gotten the first shot.

This comes as experts have repeatedly said the U.S. cannot “boost” its way out of the pandemic and instead needs more unvaccinated people to get their initial round of shots.

Boosters officially became available to all adults at the tail end of the survey period on Nov. 19. But the emergence of the omicron variant was first reported last week, prompting the CDC to recommend boosters for all adults on Monday.