A new Nightingale hospital for the North East of England has officially opened, but could end up being used solely as a "reserve capacity".
The facility in Washington on Wearside has beds for 460 people.
However, doubts have been expressed over whether anyone will be treated there as the area's permanent hospitals are coping with patient numbers.
TV presenters Ant and Dec were among celebrities who praised health workers in an opening ceremony video.
Also in the video, Health Secretary Mr Hancock paid tribute to the efforts of workers who constructed the facility in just a few weeks.
"Of course, we all hope that these extra beds will not all have to be used but I know you built this facility in a way that means you can adapt the hospital to changing clinical needs as work through the emergency and into the recovery phase continues," he said.
'With us for months'
While also acknowledging the country may have passed the peak in the number of hospital in-patients, NHS chief executive Sir Simon Stevens said it "makes complete sense to have this reserve capacity".
He warned "the reality is coronavirus is going to be with us for months if not years to come" and added the temporary hospital could play a role in convalescence and rehabilitation for patients with a range of illnesses.
Newcastle United captain Alan Shearer and England cricketer Ben Stokes were among the other names who paid tribute to health, military and construction workers in a video played during the opening ceremony.
The site, which is beside the Nissan car plant and close to the A19, was created for patients from the across the North East and North Cumbria and will be run by the Newcastle Hospitals NHS Foundation Trust as it has specialist knowledge of infectious diseases.
Last month, the trust's chief operating officer, Martin Wilson, said he did not think it would be needed as people were adequately following social distancing guidelines.
It is the latest Nightingale Hospital to open across the UK, although patient numbers have been much lower than initially anticipated.
The 4,000-bed facility at London's ExCel Arena is understood to be treating fewer than 20 patients and the site is expected to be mothballed within days.
MP Andrew Jones told the BBC a temporary hospital in Harrogate, Yorkshire, has not treated any patients, and Bristol's is believed to be empty too.
Birmingham's temporary facility can take 500 patients but also did not see anyone admitted in the days following its opening.