He has pledged to hold an inquiry into his handling of the coronavirus crisis but not yet.
“Maybe there were things we could have done differently and of course there will be time to understand what exactly we could have done, or done differently,” he told the BBC.
Johnson has come under fire from critics over his handling of the pandemic, from the high official death toll of over 45,000 and the slow roll-out of testing to a later lockdown than many other countries.
One member of the government`s scientific advisory group said the death toll could have been halved if lockdown had come a week earlier.
Johnson said the government had stuck to scientific advice “like glue”.
Asked whether lockdown came too late, he said: “When you listen to the scientists, the questions that you`ve just asked are actually very open questions as far as they are concerned.”
He said the biggest thing that the government failed to understand in the early part of the pandemic was the extent of asymptomatic transmission between people.
“(COVID-19) was something that was new, that we didn`t understand in the way that we would have liked in the first few weeks and months,” he added.