A decision on extending Covid vaccinations to 12- to 15-year-olds is expected to be announced imminently, following days of increasing pressure on the government’s vaccinations watchdog to approve the idea.

The Joint Committee on Vaccination and Immunisation (JCVI) held a long discussion on the issue on Thursday, followed by a vote.

While officials and scientists would not comment before a formal announcement, which could come as early as Friday, ministers are known to be hugely keen to press ahead with the programme, with the bulk of English schools returning this week.

The education secretary, Gavin Williamson, said on Thursday he was waiting “with bated breath” for the JCVI’s verdict, which although advisory is seen as crucial to the government’s decision on the issue.

The NHS was “ready and eager” to start vaccinating older children, Williamson said, telling Times Radio it would be “incredibly reassuring for parents to realise that they have the opportunity to choose whether it’s right for their children to have a vaccination”.

A Department for Education source said officials had not yet been told about any decision.

The Department of Health and Social Care is also known to be very keen to start the vaccinations as soon as possible, pointing to established programmes for such age groups in the US and several European countries.

Late last week the department announced that it had asked the NHS for it to start in early September, pending JCVI approval, “to be ready to hit the ground running”.

With Scottish schools already returned and Covid infection rates rising rapidly – although scientists stress it is too early to definitively link the two – Scotland’s first minister, Nicola Sturgeon, has also urged the JCVI to decide quickly.

The issue has proved a difficult one for the JCVI, with members having to weigh up not just the net health benefits to a cohort less likely to suffer from serious coronavirus ill-effects, but also whether the programme could affect other schools-based vaccination programmes. Data released last week showed that the number of teenagers in England getting vaccinated against some cancers, meningitis, septicaemia and other fatal conditions fell by 20% after the first lockdown last year.

However, increasing numbers of scientists appear to support Covid vaccinations for older children. Prof Lawrence Young, a virologist at Warwick University, said trials and evidence from other countries’ programmes had been reassuring.

“Vaccination will also reduce the ability of youngsters to spread the virus and will prevent the generation of new variants,” he said.

“Perhaps the most significant benefit of vaccinating this group is to protect their wellbeing by ensuring that there are no further disruptions to their education. This is much better, surely, than exposing children to infection and seeing what happens.”

A separate decision on a programme of third “booster” vaccines to be delivered in the autumn is, by contrast, not expected until next week at the earliest, as the JCVI is awaiting interim results from a trial about this.

Prof Saul Faust, of Southampton University, the chief investigator of the Cov-Boost study, which is looking at the effects of a third dose, said the JCVI “will have access to a limited, relevant dataset sometime next week”.

The JCVI announced on Wednesday that it had approved third injections to about 500,000 people with notably weakened immune systems. However, this was presented as not pre-empting booster jabs more generally.

If they are approved they are likely to be restricted to other more vulnerable groups, with Faust saying there was “certainly no urgency” to decide on boosters for healthy people.

The deputy chair of the JCVI, Prof Anthony Harnden of Oxford University, has already said the organisation was likely to approve booster injections in some form.

“I think it’s highly likely that there will be a booster programme,” he told the BBC. “It’s just a question of how we frame it. This will be decided over the next few weeks. I can’t definitively say that there will be, because we have not made that decision yet, but it is highly likely.”

Jeremy Hunt, the former health secretary who heads the Commons health and social care committee, has called for the UK to follow the example of Israel and widen any booster programme to all individuals eligible for a Covid vaccination.

Hunt told the Times: “I understand why there is an ethical debate about giving jabs to teenagers but surely Israel shows we should not be hanging around in getting booster jabs out to adults.”