Some care home staff are refusing the Covid-19 vaccine because of "cultural issues", the National Care Association's executive chairman has said.
Nadra Ahmed said a lack of access to the jab and not enough doses being provided by visiting doctors was also to blame for some workers not receiving it.
Her comments came as official figures are expected to confirm that all older residents in England's care homes have been offered a vaccine.
Ms Ahmed said care home staff needed to be "convinced" that the vaccine was for their safety and for the people they look after.
Speaking about why some staff had not received the jab, she told BBC Breakfast: "Some of it is to do with access and that is that people are just not able to get to where they needed to go to.
"If they've been coming into the care homes, the GPs have not had enough vaccine for the staff as well, they've just got enough for the residents, which is the priority.
"And some of it is to do with cultural issues and some is that people just don't want to have the vaccine."
The majority of care home staff who have been offered the jab are being vaccinated, but data obtained by the PA news agency in mid-January from a number of providers shows between 5% and 21% of staff offered the jab have declined it.
National Care Forum (NCF) executive director Vic Rayner said 27% of NCF member organisations reported that 70% or more of their staff had been vaccinated as of early last week.
She told Sky News that "access" to vaccinations was the main issue.
"Now clearly if you bring a vaccination team into a home there is a great opportunity to vaccinate all the staff who are there, but staff work on shifts," Ms Rayner said.
"Sometimes they might not have been available because of holidays or other issues. So I think it's about getting those staff who weren't on-site vaccinated."
Social care minister Helen Whately played down reports that some care workers were unwilling to take the vaccine.
"We know that there were some staff that were worried about the idea of having the vaccination," she told BBC Breakfast.
"But what I am hearing is that when the vaccination teams go into the care homes staff are coming forward.
"Some might be nervous but when they see their colleagues getting the vaccination, when they see that it's all right... we really are seeing good take-up from care home workers."
NHS England said figures are expected to show on Monday that people living at more than 10,000 care homes with older residents had been offered their first vaccine doses, meeting the deadline set by the Government.