Ministers are facing demands to allow younger teenagers to attend Covid vaccination centres, amid concerns that jab rates among this age group are three times lower in England than Scotland.

The vaccination rate among 12- to 15-year-olds in England currently stands at just 14.2% according to official data, compared with 44.3% in Scotland. The huge disparity has led to complaints that England has been held back by administering vaccinations solely through schools.

It comes amid rising case numbers in the UK ahead of winter, which are causing concern among scientists over what this will mean for hospital admissions and excess deaths. New daily cases have risen to their highest levels since July, at more than 40,000.

Britain’s caseload also seems high by international standards. The UK has 589.68 new cases per million, according to the latest data from Johns Hopkins University. That is more than twice the 255.24 cases per million recorded by the US and more than five times the 104.2 cases recorded by Germany. The increasing case numbers have led to some calls for the government to re-emphasise the need for basic measures such as mask wearing at higher-risk venues.

Health service insiders said school vaccination teams giving jabs to teenagers had an impossible task. The diminishing number of school nurses plays a role and persistent and growing outbreaks have meant many children are absent when jabs are given. The latest Department for Education figures show a total of 204,000 pupils were off school due to Covid.

Ministers had vowed to offer every teenager a vaccination by half term, which begins on Friday for most schools in England. However, several teachers complained that booked vaccination dates for their schools had been delayed at short notice. Some said that they were struggling to book time for their flu jabs.

A senior public health official said the original timeline was “completely unrealistic”.

Robin Bevan, head at Southend High School for Boys, said his school was still waiting for vaccination dates. “One of my jobs tonight, as we’re coming up to half term, is to write a letter to parents,” he said. “We’ve just had the harvest festival with lots of donations, we’ve had a fabulous football competition – all the kind of things you’d expect. But in the middle of it, I’ve got to say, ‘sorry, we don’t have a date yet for the Covid vaccinations. And by the way, your flu vaccinations for next week have been cancelled’.

“The real issue, as I’m seeing it, is that there just isn’t the trained, recruited capacity to run it through the school immunisation service. These are fabulous people, but they’ve been landed with something very difficult.”

It comes after education secretary Nadhim Zahawi and health secretary Sajid Javid wrote to parents urging them to encourage children to get a jab. There are multiple reports of school age immunisation service (SAIS) teams struggling to meet demand and the logistical challenges. In Scotland, teenagers have been able to visit pop-up vaccine centres.

“The difference is really stark,” said Colin Angus, a public health modeller at the University of Sheffield. “In England, vaccine rollout is being organised in schools by school nurses and immunisation teams (who handle delivery of annual flu vaccinations in schools), roles which are often understaffed, having been hit by years of cuts to local public health grants from central government and who were given only a few weeks’ notice that they had to organise the vaccination of several million schoolchildren.

“This contrasts with Scotland, where vaccination is not run through schools but where 12- to 15-year-olds can attend drop-in vaccination centres at GP clinics, pharmacies and community centres.”

Geoff Barton, general secretary of the Association of School and College Leaders, called for a change in England. “The government needs to do everything possible to boost the delivery and take-up of the Covid vaccination programme for 12- to 15-year-olds, so we would wholeheartedly support the idea of these vaccinations being made available in vaccine centres in addition to schools,” he said.

Rod Thomson, a nurse who represents the West Midlands at the Royal College of Nursing, said the number of school nurses had dwindled in the past 10 years. “Now, when we need them most, there are a third fewer school nurses,” he said. “We have also heard immunisation teams are delaying the delivery of flu immunisation because of the demands of the Covid-19 vaccine rollout.”

James Bowen, head of policy at the school leaders’ union NAHT, confirmed that many schools were still waiting to be told when they would be visited by the vaccination teams. “That October deadline [half term] has long gone,” he said. “Some schools will be waiting until the end of November for their turn – late into the autumn term.”

He said another problem was the number of pupils with Covid. For the past two and a half weeks, children aged 10-14 have been testing positive for Covid-19 at the fastest rate of any age group since mass testing was adopted in England, rising higher than 1,500 cases per 100,000 children for several days.

In January, at the peak of the second wave, case rates among people in their 20s, the most affected group, only went higher than 1,000 per 100,000 people on a few occasions. Anyone infected with Covid should wait at least 28 days before they receive a vaccine against the virus.

A spokesperson for the NHS said: “In just a few weeks, hundreds of schools have already held vaccination clinics, with over 270,000 children aged 12-15 already protected. As the rollout continues, local providers are continuing to contact schools and working with parents to agree consent so they can organise a visit.”