LONDON (Reuters) — Britain’s vaccine advisers said they were not recommending the vaccination of all 12- to 15-year-olds against COVID-19, preferring a precautionary approach in healthy children due to a rare side effect of heart inflammation.

The advice could see Britain pursue an approach different from that of the United States, Israel and some European countries, which have rolled out vaccinations to children more broadly.

However, a final decision has not been made, as the British government said it would consult medical advisers to look at other factors, such as disruption to schools.

Many politicians and some scientists have spoken out in favor of vaccinating more children amid concerns that COVID-19 could spread in schools reopening after the summer holidays, further disrupting education.

Britain has reported more than 133,000 deaths from COVID-19 and nearly 7 million cases, and while transmission among children can be high, they are rarely severely ill from the disease.

On Friday, the Joint Committee on Vaccination and Immunisation (JCVI) said children with underlying conditions that made them more at risk from COVID-19 should get vaccinated.

For healthy children, there was still a small benefit from receiving COVID-19 vaccination, and advisers said the risk-benefit was “finely balanced.”

However, the JCVI said it wanted more information on the long-term effects of rare reports of heart inflammation, known as myocarditis, in young people following vaccination with Pfizer’s shot.

Myocarditis is rare and normally mild, with patients usually recovering in a few days.

“Of course, these vaccines do work and would be beneficial to children in terms of preventing infection and disease, but the number of serious cases that we see of COVID in children this age are really very small,” JCVI member Adam Finn told Reuters.

“There are uncertainties about the long-term implications of (myocarditis), and that makes the risk-benefit balance for these children really quite tight and much tighter than we would be comfortable to make the recommendation.”

UK Secretary of State for Health and Social Care Sajid Javid, who sets policy for England, and his counterparts from Scotland, Wales and Northern Ireland, wrote to the chief medical officers (CMOs) of the four nations, asking for further advice, “including on educational impacts.”

“Given the importance of this issue, we would be grateful if you could provide your advice as soon as possible,” the four health ministers said in a letter to the CMOs.

The JCVI is also expected to advise on a potential booster vaccine program for the elderly and vulnerable, which could start this month.

Finn said there would be an update on boosters “within the next few days.”