Students cannot be guaranteed they will be able to return to university campuses after the Christmas break, amid fears they could unintentionally spread Covid-19 across the country.

The government announced on Tuesday students in England will be able to return home during a “travel window” between December 3 and December 9.

The Department for Education (DfE) said “staggered departures” should be arranged to prevent crowds of students on public transport flocking home at the same time.

Some students will be able to take rapid coronavirus tests, which can turn around results within an hour, to ensure they are not positive for the illness before travelling.

All teaching is due to be moved online by December 9 “at the very latest”.

But the DfE would not comment on whether similar procedures would be put in place when the Spring term begins in mid-January, and whether its intention was for students to return to campuses.

Instead the department pointed to the guidance published on Tuesday that said only: “Following the end of term break, our top priority for January will be the welfare of students, staff and the communities around higher education providers.

“We are looking to utilise mass testing to make the return to higher education as safe as possible, and will provide further guidance in due course, considering future developments and the relevant scientific advice.”

Jenny Harries, deputy chief medical officer, said the “mass movement of students across the country” at the end of term presented “a really significant challenge within the Covid-19 response”.

“The measures announced today will help minimise that risk and help students get home to their families as safely as possible for Christmas,” she said.

“It is crucial that students follow the guidance in order to protect their families and the communities they return to.”

It came as England’s chief medical officer, professor Chris Whitty, warned in a letter to NHS staff that the winter would be “gruelling”.

More than 50,000 people in the UK have now died within a month of testing positive for coronavirus.

Tuesday saw the UK’s daily death toll surpass 500 for the first time in almost six months but Wednesday’s daily increase of 595 is the largest since May 12.

But there is one ray of hope, as Pfizer and BioNtech announced a major breakthrough in the race for a Covid-19 vaccine, with early results suggesting their jab is 90% effective.