Vallance told a virtual parliamentary Health and Social Care Committee hearing that it is difficult for the UK government to get a very granular estimate of the so-called R rate, adding: “that's true in other countries as well.”
"We will, I hope, get a better rate when we can measure it more directly by measuring rates of infections within the community with large population based surveys,” he added.
Vallance said that the R rate needs to be below one, and said that there is “a little bit of regional variation” in the R rate across the UK.
“It needs to be below one because as long as its below one that means the epidemic is reducing and then instead of talking about the doubling [of infection] you’re talking about the halving time of the epidemic and obviously the lower the R the shorter the halving time ... anything below one will be a reducing epidemic,” he explained.
Vallance and England’s deputy chief medical officer Jenny Harries faced questions from the committee on the UK government’s progress towards easing lockdown restrictions.
The UK must review its lockdown measures by Thursday this week, but is not expected to announce major changes at this point.