Mr Johnson was speaking after it was revealed only 2,000 out of some half a million frontline NHS workers in England had been tested.
The PM said the government needed to "massively ramp up" testing so that NHS staff who are self-isolating unnecessarily could return to work.
Mr Johnson, who is self-isolating in Downing Street after contracting the virus himself, has faced widespread criticism over his government's testing strategy.
Outpatient dates go on phone or video at hospitals
The trust that runs hospitals around Morecambe Bay says some outpatients will be "seen" by video link or over the telephone because of the COVID-19 pandemic.
The trust’s outpatient departments at the Royal Lancaster Infirmary, Westmorland General Hospital (pictured) in Kendal and Furness General Hospital, along with health centres at Queen Victoria Hospital in Morecambe and Ulverston Community Health Centre are cutting back on services to reduce the risk of spreading coronavirus.
Two of latest virus deaths were at Barrow hospital
More details have been made public of deaths of patients who had given positive tests for coronavirus at hospitals run by the Morecambe Bay hospitals trust.
The trust says that two were a man aged 79, and a woman, 81, at the Furness General in Barrow, while the third was a woman aged 76 at the Royal Lancaster Infirmary, which serves parts of South Cumbria.
All of them officials said, had other underlying health conditions.
Circus clowns find a way to work from home
Brothers and neighbours Mooky and Mr Boo haven't let coronavirus social distancing stop them from practising their routine.
They've found a way to rehearse at a safe distance - and entertain the neighbours while they're at it!
One-and-a-half million people in England have been identified as being extremely medically vulnerable and the government will distribute free food parcels every week to more than 50,000 who have no family or friends to help them.
The identical parcels contain essential non-perishable supplies like pasta, cereal, fruit, tea bags, potatoes and tinned goods, as well as toilet paper.
A food distribution company will deliver the packs to people's doorsteps, although in some cases local authorities, charities or emergency services may help out.