Three in 10 care home staff have not been vaccinated against Covid-19 despite being in the top four priority groups, according to data from NHS England.
More than 435,000 workers in care homes for older adults are eligible in England, but only 304,600 have received a first dose.
In London, only 52% of staff have had a jab, rising to 75% in the South West.
The UK target of vaccinating 15 million people was met at the weekend.
But these figures, up to 14 February, suggest there are large groups of care workers, who are in the top four priority groups, who have still not come forward.
Some care home staff have previously said they refused the vaccine because of "cultural issues", but organisations representing care providers say they must be convinced to have one - to protect them and the services they work in.
Some 95% of care home residents in England - who are also prioritised - have been vaccinated, with all regions above 93%.
Four groups - care home workers and residents, frontline health workers, the over-70s and clinically extremely vulnerable people - have been prioritised for vaccines since the UK's mass vaccination programme started in December.
This data shows that 1.02 million health workers in England have been vaccinated with a first dose.
This figure, which does not include agency staff, is equivalent to 88% of patient-facing staff.
And 1.8 million of those at very high risk of serious illness from Covid-19 (deemed clinically extremely vulnerable) have also been given a vaccine.
People in this group have specific health conditions or are undergoing certain types of treatment which increases their risk from coronavirus.
A total of 2.2 million people in England are currently in this group which has been asked to shield, although an extra 1.7 million are expected to be added to the list based on other factors.
A campaign to persuade people belonging to ethnic minorities to have a Covid vaccine is being shown across the UK on TV channels on Thursday. Official figures suggest they are less likely to be vaccinated.
The latest evidence comes from a study of GP records looking at vaccine take-up.