Which COVID policies are most effective? A Bayesian analysis of COVID-19 by jurisdiction

Abstract

This paper reports the results of a Bayesian analysis on large-scale empirical data to assess the effectiveness of eleven types of COVID-control policies that have been implemented at various levels of intensity in 40 countries and U.S. states since the onset of the pandemic. The analysis estimates the marginal impact of each type and level of policy as implemented in concert with other policies. The purpose is to provide policymakers and the general public with an estimate of the relative effectiveness of various COVID-control strategies. We find that a set of widely implemented core policies reduces the spread of virus but not by enough to contain the pandemic except in a few highly compliant jurisdictions. The core policies include the cancellation of public events, restriction of gatherings to fewer than 100 people, recommendation to stay at home, recommended restrictions on internal movement, implementation of a partial international travel ban, and coordination of information campaigns. For the median jurisdiction, these policies reduce growth rate in new infections from an estimated 270% per week to approximately 49% per week, but this impact is insufficient to prevent eventual transmission throughout the population because containment occurs only when a jurisdiction reduces growth in COVID infection to below zero. Most jurisdictions must also implement additional policies, each of which has the potential to reduce weekly COVID growth rate by 10 percentage points or more. The slate of these additional high-impact policies includes targeted or full workplace closings for all but essential workers, stay-at-home requirements, and targeted school closures.

Fig 1. COVID policy levels by week based on OxCGRT database.

Policies C1-C6; continued in Fig 2.

Fig 2. COVID policy levels by week based on OxCGRT database.

Policies C7, C8, H1-H3; continued from Fig 1.

Fig 3. Marginal effect sizes of policy measures on reducing weekly growth rates.

Bars = median estimate by policy level; Lines = 95% intervals for maximum policy level.

Fig 4. Weekly rate of new infections and their growth by jurisdiction as of November 22, 2020.

Dots = median estimates; Lines = 95% intervals.

Fig 5. Growth rate g^(base) after jurisdictions have started to implement one of the base policies (level 1 of C1-C4).

A lower number indicates a higher effectiveness to contain the virus. The total growth rate g_it of the virus is the number in this chart minus the sum of the effects of implemented policies in Fig 3. Lines = median estimates; Grey bands = 95% intervals

Fig 6. Effects of a set of core policies on weekly growth rate g by quantile of g^(base) among all jurisdictions.

Core policies include the cumulative effects of C3–2, C4–3, C6–1, C7–1, C8–3, H1–2, H2–2, and H3–2. Dots = median estimates; Lines = 95% intervals.