Good morning and welcome to The Independent’s rolling coverage of the Covid pandemic.

Covid cases and hospitalisations are rising in England – and experts don’t know why.

The lifting of all Covid restrictions has made it more difficult to properly track and understand the country’s epidemic, scientists have warned the government following a recent and sudden rise in hospital admissions.

Our science correspondent Sam Lovett reports:

Health chiefs have revealed they are officially monitoring a new version of Covid-19 – which has been nicknamed “stealth Omicron”.

The UK Health Security Agency has marked BA.2 a “variant under investigation” – one level below a “variant of concern” – after early data suggested it may be both more transmissible and better able to evade vaccines than previous strains of the killer virus.

A rise in Covid infections was to be “expected” following the easing of Covid-19 restrictions in England, the Health Secretary has said.

Sajid Javid said that the UK remains in a “very good position” but he urged adults eligible for a booster vaccine to come forward and get the jab.

Ella Pickover has the story:

France has lifted most Covid-19 restrictions, abolishing the need to wear face masks in most settings and allowing people who are not vaccinated back into restaurants, sports arenas and other venues.

The move had been announced earlier this month by the French government based on assessments of the improving situation in hospitals and following weeks of a steady decline in infections.

It comes less than a month before the first round of the presidential election scheduled on April 10.

But in recent days, the number of new infections has started increasing again, raising concerns from some scientists it may be too soon to lift restrictions.

The number of new infections has reached more than 60,000 based on a seven-day average, up from about 50,000 a week before.

Starting from Monday, people are no longer required to show proof of vaccination to enter places such as restaurants and bars, cinemas, theatres, fairs and to use interregional transport.

The so-called vaccine pass had taken effect at the end of January.

In hospitals and nursing homes, unvaccinated people must provide a recent negative test or proof of recent recovery to enter.

Wearing masks is no longer required in schools, businesses and offices.

Greek prime minister Kyriakos Mitsotakis has tested positive for COVID-19, he said in a video message on Instagram on Monday.

"I tested positive this morning and therefore will isolate at home and work from there," Mitsotakis said.

Mitsotakis met with Turkish President Tayyip Erdogan in Istanbul on Sunday.

China has banned most people from leaving a coronavirus-hit north-eastern province and mobilised military reservists as the fast-spreading “stealth Omicron” variant fuels the country’s biggest outbreak since the start of the pandemic two years ago.

The National Health Commission reported 1,337 locally transmitted cases in the latest 24-hour period, including 895 in the industrial province of Jilin province.

A government notice said that police permission would be required for people to leave the area or travel from one city to another.

The hard-hit province sent 7,000 reservists to help with the response, from keeping order and registering people at testing centres to using drones to carry out aerial spraying and disinfection, state broadcaster CCTV reported.

Hundreds of cases were reported in other provinces and cities along China’s east coast and inland as well.

Beijing, which had six new cases, and Shanghai, with 41, locked down residential and office buildings where infected people had been found.

A single dose of the Pfizer Covid-19 vaccine can reduce infections among children, a new study suggests.

And if a child gets Covid-19 after being vaccinated they are “likely to have a milder disease”, researchers from King’s College London and ZOE Ltd said.

While the Covid-19 vaccines have been shown to ward off serious disease and death, questions have arisen over their ability to reduce the spread of infections.

The latest study examined the effectiveness of a single dose of the Pfizer/BioNTech Covid vaccine in children.

Cathy Gardner and Fay Harris have taken legal action against Health Secretary Sajid Javid, NHS England and Public Health England.

Two judges began overseeing a hearing - which is due to last six days - at the High Court in London on Monday.

Lawyers representing the three defendants are fighting the claim.

Two women whose fathers died from Covid-19 in care homes have begun a High Court fight after complaining about Government “failure” to protect residents during the pandemic.

The site in Sunderland, Tyne and Wear, had been a research centre but was handed over to the NHS to use at the beginning of the pandemic as a temporary hospital.

It then became a vaccination centre but is now expected to be vacated next month, with the NHS continuing its vaccination programme on a local level in the area.

But the move has caused concern for city councillors about the potential impacts residents, and they have questioned why other local mass vaccination sites in the North East will continue.

The building was recently put on the market and is expected to be ready for a new occupier by summer 2022.

“I really hope we haven’t been kept in the dark by any of the national authorities,” said councillor Michael Butler, vice-chair of Sunderland City Council’s Health and Wellbeing Scrutiny Committee.

“I’m sure the other areas have primary care networks working really hard and chemists and pharmacies doing the vaccinations.

“It’s quite worrying certainly as an individual representing the residents of Sunderland that the city will no longer have a mass vaccination centre and hopefully it doesn’t undo all the great work that everyone has done.”

Concerns have been raised over plans to decommission a Nightingale Hospital.