Herd immunity was a "very dangerous" strategy for dealing with the Covid pandemic that would have led to a "extraordinarily high loss of life", Professor Sir Chris Whitty has told the pandemic inquiry.
The chief medical officer said that public debate around the policy had caused "confusion" during the early stages of the pandemic.
Herd immunity refers to the indirect protection from an infectious disease that happens when a population is immune either through vaccination or infection. In the Covid pandemic, employing the strategy would have meant allowing large numbers of people to be infected.
Media reports during the period suggested that former Prime Minister Boris Johnson and other Downing Street officials were considering the strategy.
In March 2020, Mr Johnson told ITV that “one of the theories is that perhaps you could take it on the chin, take it all in one go and allow the disease, as it were, to move through the population, without taking as many draconian measures”.
Addressing the inquiry on Wednesday, Sir Chris said it would have been “inconceivable” to create herd immunity through natural infection because “it would have led to extraordinarily high loss of life.”
“We had no idea whether, even in a theoretical situation, the population would by natural infection even get to the herd immunity threshold.”
He added: “People who’ve got higher risks – older citizens, people with disabilities, people with immunosuppression and so on – (would have) very significant risks of mortality, so the impact of that on mortality would be very severe.”
Sir Chris said that, in his view, the only rational policy response was where “you would ever achieve aim to achieve herd immunity is by vaccination”.
He added that there was a “large amount of chatter” about herd immunity by “people who had at best half-understood the issue”.
The inquiry has previously heard how Mr Johnson flirted with the idea of "letting Covid rip" through the population in the weeks leading up to the second national lockdown.
He is said to have referred to a “whisky and a revolver” during a meeting with officials in October 2020 and spoke about “medieval measures” to tackle the pandemic.
The remarks were detailed in the notebook of the then-chief scientist Sir Patrick Vallance as Mr Johnson’s government mulled whether to impose the lockdown.
Dame Jenny Harries, the current chief executive of the UK Health Security Agency (UKHSA), said in 2021 that she had "never been in any government meeting where herd immunity was put forward".
But former No10 chief adviser Dominic Cummings said he found her remark "astonishing" in a written statement given to the inquiry last month.
“Given the volume of such charts [in March 2020] and what everybody who was there know was discussed, it is astonishing that Jenny Harries [said this]…”
