Timing is everything: the relationship between COVID outcomes and the date at which mask mandates are relaxed

Shoukat, A.; Galvani, A. P.; Fitzpatrick, M. C.

Importance Several states including Texas and Mississippi have lifted their mask mandates, sparking concerns that this policy change could lead to a surge in cases and hospitalizations. Objective To estimate the increase in incidence, hospitalizations, and deaths in Texas and Mississippi following the removal of mask mandates, and to evaluate the relative reduction of these outcomes if policy change is delayed by 90 days. Design, Setting, and Participants This study uses an age-stratified compartmental model parameterized to incidence data in Texas and Mississippi to simulate increased transmission following policy change in March or June 2021, and to estimate the resulting number of incidence, hospitalizations, and deaths. Main Outcomes and Measures The increase in incidence, hospitalizations, and deaths if mask mandates are lifted on March 14 compared to lifting on June 12. Results If transmission is increased by 67% when mask mandates are lifted, we projected 11.39 (CrI: 11.22 - 11.55) million infections, 170,909 (CrI: 167,454 - 174,379) hospitalizations, and 5647 (5511 - 5804) deaths (Figure 1) in Texas from March 14 through the end of 2021. Delaying NPI lift until June reduces the average number of infections, hospitalizations, and deaths by 36%, 65%, and 62%, respectively. Proportionate differences were similar for the state of Mississippi. Peak hospitalization rates would be reduced by 79% and 63% in Texas and Mississippi, respectively. Conclusions and Relevance Removal of mask mandates in March 2021 is premature. Delaying this policy change until June 2021, when a larger fraction of the population has been vaccinated, will avert more than half of the expected COVID-19 hospitalizations and deaths, and avoid an otherwise likely strain on healthcare capacity.