Britain is once again at the peak of a coronavirus surge, just over three months after all coronavirus restrictions were lifted on what Prime Minister Boris Johnson hailed as “Freedom Day.”

Cases have stayed at high levels since then, with more than 20,000 new cases recorded each day. There are almost 9,000 Britons hospitalized with COVID-19 — the highest level since March, when the United Kingdom was in the midst of a long national lockdown.

Unlike the rises and falls of previous periods of infection, the most recent wave shows the positive impact of Britain’s vaccination rollout: Far fewer COVID hospital admissions and deaths have followed the rise in cases than in previous waves. Still, health experts contend that the ongoing hospitalizations and deaths are burdening overstretched hospitals and could be reduced with basic measures.

Tim Spector, a professor at King’s College London, who has been leading a major study of COVID symptoms since the start of the pandemic, said it is hard to predict whether high levels of transmission will continue. One reason for the uncertainty, he said, is that public behavior, led by government guidance, is very different now than in previous surges. “In past waves, there’s been a general panic and reduction in mobility,” he said.

England has some of the loosest coronavirus protections in Europe since July 19, when it lifted all legal restrictions, including mandatory mask-wearing. In a recent survey by YouGov and Imperial College London, 21% of Britons said they rarely or never wear a face mask in public — about four times as many as in Italy and Spain.

Despite the extended surge in cases, the U.K.’s Scientific Advisory Group for Emergencies recently said that behaviors in Britain are closer to pre-pandemic levels than at any time since March 2020.

The current surge is being primarily driven by high levels of infection in school-age children, with more than one-third of all recent cases being reported in those younger than 15.

Unlike most of Europe, the U.K. was slow to approve vaccines for adolescents. The recommendation of a single dose of the Pfizer-BioNTech vaccine for 12- to 15-year-olds was not announced until mid-September — weeks after many students had returned to school from summer vacation. So far, just 21% of 12- to 15-year-olds are vaccinated in England, compared with 80% of adults.