All health and care staff should be routinely tested for Covid-19 once or twice a week, according to one of the UK’s most eminent scientists, Sir Paul Nurse, whose team’s research suggests 45% of staff were infected with coronavirus at the peak of the pandemic in England, most of whom showed no symptoms.

Giving evidence to the Commons health and social care select committee, Nurse, who turned the Crick Institute he heads into a testing laboratory, said his team had told ministers that frequent, routine testing was essential to ensure the safety of health and care staff and give the public the confidence to go into hospitals.

“My colleagues in the Crick contacted Downing Street in March, wrote to minister [Matt] Hancock in April, emphasising two main things: the importance of regular systematic testing of all healthcare workers, including not only frontline doctors and nurses but support staff, ambulance drivers and other healthcare providers, such as the care homes, GP surgeries, community nurses and the like. These all need to be tested.

“At the height of the pandemic, our own research – and of course that only backs up what’s been done elsewhere – is that up to 45% of healthcare workers were infected. And they were infecting their colleagues … reinfecting patients, yet they weren’t being tested systematically.”

The second point they made to Hancock, he said, was that high numbers of people were testing positive without symptoms. “Again, our own research has shown that nearly 40% of healthcare workers at that time were infected but had no symptoms. So this was a real, major failure. In the healthcare environment, we weren’t providing proper protection. And it’s important.”

He said healthcare workers “deserve to work in a safe environment. I mean, some of them are dying because of what they do.” Routine testing would be important before a possible second wave in the autumn and winter, he said.

He rejected the argument that some tests showed people were infected when they were not. His lab had seen no more than one false positive out of 5,000 tests, he said.

Nurse said it was not always clear who was in charge in the crisis. “It’s not always been clear at least to me and my colleagues as to who is in charge exactly and who has been making decisions.”

Sir Jeremy Farrar, the head of Wellcome, said the UK had not been prepared for the pandemic. Like much of the rest of the world, it had neglected public health since the first Sars outbreak in 2003, he said.

“We’ve underestimated the warning calls from Sars 1 through Ebola, through Zika, through the [flu] pandemic of 2009. Maybe the world became a little bit cynical. Emerging infections were not going to cause the devastation that some people had said they would. And we let down our guard, and we didn’t realise the power of infectious diseases,” he said.

“So I think critically we need to look at that period prior to December 2019 coming into January and February, which is what I regard as the absolute critical two months.”

It was very clear by 20 January that the virus was not like Sars 1, he said. There was asymptomatic transmission, it was highly infectious and it caused a range of illness, from mild to very severe. “It was an animal infection that humans have no immunity to, and we had no diagnostics no treatments and no vaccines,” Farrar said.

“I think the lessons that Korea, Singapore, Vietnam had learned from previous epidemics were well implemented. And they acted quicker. I think the UK was slow to put in place testing, to put in place extra clinical capacity, and to make sure that healthcare workers were protected with PPE. And as a result, subsequent events led to the epidemic taking off in a way in the UK which was not the same as in Korea, Germany, or even Singapore and Vietnam.”

Farrar said the UK should have significantly increased testing in January and February. Instead, it took the decision that there was too much transmission of the virus in the community and went for lockdown instead. “In retrospect, I think that was a mistake,” he said.

That had been the advice of the WHO and it was what Germany, South Korea, Singapore and Vietnam had done – countries that have suffered fewer deaths. “That would have been a better option, to ramp up the testing in February,” he said.

“It goes back to my comment about the eight weeks in January and February, when I think there was not enough urgency. And if I again now look back on my time on the Sage committee, I regret that Sage wasn’t more blunt in its advice and wasn’t more robust.” But it was not in Sage’s remit to hold anybody to account, he said.