The effectiveness of the three tier system of local restrictions for control of COVID-19

Despite it being over 10 months since COVID-19 was first reported to the world and it having caused over 1.3 million deaths it is still uncertain how the virus can be controlled whilst minimising the negative impacts on society and the economy. On the 14th October England introduced a three-tier system of regional restrictions in an attempt to control the epidemic. This lasted until the 5th November when a new national lockdown was imposed. Tier 1 was the least and tier 3 the most restrictive tiers. We used publicly available data of daily cases by local authority (local government areas) and estimated the reproductive rate (R value) of the epidemic over the previous 14 days at various time points after the imposition of the tier system or where local authorities were moved into higher tiers at time points after reallocation. At day 0 there vas very little difference in the R value between authorities in the different groups but by day 14 the R value in tier 3 authorities had fallen to about 0.9, in tier 2 to about 1.0 and in tier 1 the R value was about 1.5. The restrictions in tier 1 had little impact on transmission and allowed exponential growth in the large majority of authorities. By contrast the epidemic was declining in most tier 3 authorities. In tier 2, exponential growth was being seen in about half of authorities but declining in half. We concluded that the existing three tier system would have been sufficient to control the epidemic if all authorities had been moved out of tier 1 into tier 2 and there had been more rapid identification and transfer of those authorities where the epidemic was increasing out of tier 2 into tier 3. A more restrictive tier than tier 3 may be needed but only by a small number of authorities.