Two in five 16 to 17-year-olds in Northampton have received a first dose of the coronavirus vaccine, figures reveal.
It comes as pupils across England return to school after the summer holidays, amid a warning over a potential rise in cases.
While a new mass-testing policy has been introduced to tackle outbreaks in schools, the Government is also calling on those eligible to get a Covid jab.
Public Health England data shows 2,261 people aged 16 and 17 in Northampton had received a jab by September 4 – 39% of the age group, based on the number of people on the National Immunisation Management Service database.
That was much lower than the 49% average across England.
Uptake varied widely across the country – in Hart in the South East, 72% of 16 to 17-year-olds had received a jab by September 4, while the lowest uptake, 23%, was recorded in in the London borough of Hackney.
Those aged 16 and 17 became eligible for a vaccine last month and pop-up vaccination centres were set up at events such as music festivals to encourage uptake.
But Prime Minister Boris Johnson said the UK needed to speed up vaccinating youngsters in the age group, who are “a very important group for potential transmission”.
“There are still some who need that protection and I would just urge everybody who hasn’t yet had a jab to go and get one,” he added.
The re-opening of schools in Scotland last month is believed to have contributed to a rise in cases there and there are fears the same will happen in England.
Paul Whiteman, general secretary of NAHT school leaders’ union, said schools had worked hard over the summer to ensure a safe environment for the return of pupils, but poor guidance remained an issue.
He said: “The warnings from scientists about a potential rise in cases when schools return mean that it is essential the Government responds rapidly should the data suggest it is necessary to implement additional safety measures in schools."
The Association of School and College Leaders said though the Government no longer advised the use of face coverings for pupils, schools could still make their own decisions on the matter.
Geoff Barton, general secretary, said: “A certain degree of caution is hardly surprising given the bitter experience of the past 18 months, when many schools and colleges have had to cope with two periods of partial closure and large numbers of pupils self-isolating at other times.”
The Department for Education said contingency measures were in place if schools were to see an increase in cases.
A spokesman said: "Schools have clear guidance on how to maintain good ventilation and keep classes warm enough, and the 300,000 carbon dioxide monitors we are providing – backed by £25 million – will begin rolling out from this week, giving schools another tool in their arsenal to keep the virus out of classrooms."
Discussions on whether to allow 12 to 15-year-olds who do not have underlying health conditions to be vaccinated are also ongoing.
The Joint Committee for Vaccination and Immunisation said the benefit is considered too small to support a rollout – but Professor Chris Whitty and the three other chief medical officers in the UK are now reviewing the wider benefits of vaccinating the age group.