If you take the numbers from the UK (here https://coronavirus.data.gov.uk/ https://coronavirus.data.gov.uk/) and filter to just the 2nd and 3rd waves (testing w

If you take the numbers from the UK (here https://coronavirus.data.gov.uk/ https://coronavirus.data.gov.uk/) and filter to just the 2nd and 3rd waves (testing was poor in 1st wave; lots of people are vaccinated in the 4th) and compute the autocorrelation function between positive tests and deaths, you see a peak around 14 days.