The analysis, which its authors say is the most comprehensive on the topic to date, backs up clinical reports that show children and teens are less likely to be hospitalized or face severe effects from the virus. Covid-19 does increase the chance of serious illness in the most vulnerable children — those with complex disabilities and severe existing medical conditions — but even in those cases the risks are smaller compared with adults.

In England, the highest rates of infection in recent weeks were seen in those ages 15 to 29, with the fastest jump in positive cases week-on-week among children ages 5 to 14. With 68% of adults in the U.K. having received at least one shot and more than 50% fully vaccinated, the increase highlights the role children may be playing in transmission.

“It is reassuring that these findings reflect our clinical experience in hospital — we see very few seriously unwell children,” Elizabeth Whittaker, senior clinical lecturer in pediatric infectious diseases and immunology at Imperial College London, said in a statement. “We hope this data will be reassuring.”

Though the data only measure the period up to February, the situation hasn’t changed recently with the proliferation of the delta variant, Whittaker said.

Under 18s in England had about a 1-in-50,000 chance of being admitted to intensive care with coronavirus during the first year of the pandemic, one study in the analysis found. A number of conditions that were previously thought to increase the risks of Covid-related illness, like active asthma or cystic fibrosis, brought “very little risk,” researchers said at a press briefing.

“There’s a general feeling among pediatricians that probably too many children were shielded in the first elements of the pandemic and that there’s probably very few children that need to shield according to these data,” Russell Viner, a professor of child and adolescent health at University College London, said at the briefing. He was senior author of two of the studies involved.

The analysis is based on three papers that haven’t yet been peer reviewed, led by researchers at UCL, University of Bristol, University of York and the University of Liverpool. Preliminary findings will be submitted to Britain’s Joint Committee on Vaccination and Immunization, the Department for Health and Social Care and the World Health Organization to help inform policies on shielding and vaccinations for under-18s in Britain and elsewhere, the statement said.

While most children have been spared the worst effects of the disease — showing mild to no symptoms — a small number of severe cases have led to hospitalization and death. A growing cohort of kids is also suffering from so-called long Covid — residual symptoms after infection ranging from extreme fatigue to depression. With children now driving the spread of cases in many countries, governments have come under pressure to speed up inoculations for younger people.

The studies on young people didn’t look at the impact of long Covid, according to the statement.

The U.S. is one of the few countries offering Covid-19 vaccines to children ages 12 and over — the only group for which there’s clinical data so far. The U.K. has approved the Pfizer Inc.-BioNTech SE shot for adolescents, but hasn’t rolled it out yet. Europe’s drugs regulator also authorized the Pfizer vaccine, though only France and a limited number of other countries are administering it.