SARS-CoV-2 Spread Under the Controlled-Distancing Model of Rio Grande do Sul, Brazil

In early 2020, the government of Rio Grande do Sul established a public-health assessment-response framework to halt the spread of SARS-CoV-2, called controlled-distancing model (CDM). This framework subdivided the state in 21 regions where it evaluated a composite index of disease transmission and health-service capacity. Updated on a weekly basis, the index placed regions on a color-coded scale of flags, which guided adoption of non-pharmaceutical interventions. We aim to evaluate the extent to which the CDM accurately assessed transmission and the effectiveness of its responses throughout 2020. We estimated the weekly effective reproduction number (Rt) of SARS-CoV-2, for each region, using a renewal-equation-based statistical model of notified COVID-19 deaths. Using Rt estimates, we explored whether flag colors assigned by the CDM either reflected or affected SARS-CoV-2 dissemination. Flag assignments did reflect variations in Rt, to a limited extent, but we found no evidence that they affected Rt in the short term. Medium-term effects were apparent in only four regions after eight or more weeks of red-flag assignment. Analysis of Google movement metrics showed no evidence that people moved differently under different flags. The dissociation between flag colors and the propagation of SARS-CoV-2 does not support the claim that non-pharmaceutical interventions are ineffective. Our results show, however, that decisions made under the CDM framework were ineffective both for influencing the movement of people and for halting the spread of the virus.