How robust was the evidence for lockdown?

Ever since it was first published in May, the Office of National Statistics’ weekly infection survey has been looked upon as the gold standard of Covid data. It is based on swab testing of a large, randomised sample of the population who are tested repeatedly to see if they are infected with the virus – the results from which are scaled up to arrive at an estimate of incidence of the disease in the population as a whole. 

Being a randomised sample, it does not suffer from the drawback of the daily Public Health England figures for confirmed infections – which are heavily influenced by how many tests are being conducted. As the number of tests has expanded, so, too, the number of confirmed infections has risen.

However, the most recent edition of the ONS’ infection survey shows just how fickle the data can be – and how difficult it must be for the government to make decisions when data is so subject to change.