Modelling the impact of the tier system on SARS-CoV-2 transmission in the UK between the first and second national lockdowns

Study found tier 3 reduced transmission by 23% (21-25%), tier 2 by 6% (5-7%); tier 1 had negligible effects. The relatively small effect sizes show interventions at least as stringent as tier 3 are required to supress transmission, at least until widespread effective vaccination.

BMJ Open