Some 6% of people aged 80 and over in England may not have received any doses of Covid-19 vaccine, new data suggests.
The figure is the equivalent of around one in 17 over-80s, or just over 171,000 people, with 47,000 of them in London.
Other age groups among the over-50s are likely to have a much lower percentage of unvaccinated individuals, with estimates of 0.5% for 70 to 79-year-olds, 2.3% for 60 to 69-year-olds and 4.9% for 50 to 59-year-olds.
The data has been published by NHS England and covers vaccinations delivered up to July 4.
The Government has said all adults in England will have been offered a first dose of Covid-19 vaccine by July 19.
The latest figures suggest there may be pockets of vaccine hesitancy in some parts of the country among the very old.
People aged 80 and over were among the earliest to be offered a first dose of Covid-19 vaccine in December last year.
There is also some way to go before the proportion of adults in younger age groups with one dose of vaccine reaches similar levels to those in the over-50s.
Some 78.2% of 30 to 39-year-olds are now estimated to have had their first dose, along with 60.3% of 18 to 29-year-olds.
The estimate for 40 to 49-year-olds is 87.8%.
For people in England who have received both doses of vaccine, the estimate for those aged 80 and over is 91.9%, suggesting around one in 12 is not fully vaccinated.
Some 98.0% of 70 to 79-year-olds are likely to have both jabs, along with 94.8% of 60 to 69-year-olds, 90.0% of 50 to 59-year-olds, 61.7% of 40 to 49-year-olds, 31.9% of 30 to 39-year-olds and 19.3% of 18 to 29-year-olds.