Some 79.4% of residents and 34.3% of staff at older age care homes in England have had their booster as of December 12, according to data from NHS England.
This falls to 24.7% of staff in care homes in the capital.
A fifth (20.6%) of residents (65,036 residents) and 65.7% of staff (301,400 staff) have not been recorded as having received their booster by this point.
People are eligible for their booster if they received their second dose at least three months ago, while those who test positive for coronavirus must wait 28 days.
They are based on responses from 98.2% of older age care homes, 96.6% of younger age care homes, 87.1% of domiciliary care providers and 25.0% of local authorities.
NHS England said the percentages for those who have received a booster, therefore, may be underestimated.
There will be some staff whose vaccination status is unknown while there may also be a time lag in some vaccinations being reported, it added.
The data shows that 30.1% of staff and 63.9% of residents in younger age care homes have received their booster dose.
This leaves 60,258 staff and 12,837 residents not recorded as having received it.
In domiciliary care, 78.3% of staff have not been recorded as having had a booster.
Boosters for just 2.2% of staff working in other settings, such as non-registered providers and those employed by local authorities, have been recorded in the figures.