The coronavirus pandemic is not over and cases among older people are increasing, an expert has warned.

Dr Jenny Harries, chief executive of the UK Health Security Agency (UKHSA), sounded the alarm after data showed that an increasing number of people aged 55 and older have COVID-19.

About one in 35 people (2.88%) of people in England were infected between 8 February to 1 March, according to the latest React-1 study.

The figure decreased from 4.41% in the period between 5 January and 20 January – but was also the second-highest recorded rate of cases since the study started in 2020.

Professor Paul Elliot, director of Imperial College London’s React programme, said the data shows an “uptick” in hospital admissions.

Dr Harries said: “These data confirm that cases have declined substantially following the peak of the Omicron wave.

“However, the increasing presence of the BA.2 sub-lineage of Omicron and the recent slight increase in infections in those over 55 show that the pandemic is not over and that we can expect to see COVID circulating at high levels.”

Asked whether the BA.2 sublineage of the Omicron variant could lead to a surge in cases, Prof Elliott said it is more transmissible and the data – including the number of hospitalisations – needs to be monitored closely.

“At the moment, we’re possibly seeing the beginning of an uptick, but we don’t know where it’s going to go,” he said.

Prof Elliot said the figures could indicate that infections are starting to increase in England.

The study’s authors suggested increasing cases among those aged 55 and over could be due to more socialising after restrictions were eased and the effectiveness of booster jabs wearing off.