Using a natural experiment examining the association between the state-wide mandate orders for face cover in public and the daily confirmed COVID-19 cases from all states, a study reported that community-wide mask-wearing could have accounted for declines in COVID-19 growth rates in the US during Spring 2020 9. Two meta-analyses of respiratory diseases caused by coronaviruses, including Severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and SARS-CoV-2, demonstrated that mask-wearing and social distancing effectively reduced viral transmission 7, 8. Mask-wearing and social distancing are the two critical measures to mitigate the transmission of respiratory diseases 5, 6. The state-wide policy required ongoing monitoring of these metrics, and recommended the reinstatement of restrictions in a given region if the criteria were exceeded 5. However, due to a concern for a potential resurgence of cases, the reopening in each region of the state was contingent on meeting several criteria, including maintaining 30% hospital and ICU bed capacity region-wide. New York State (NYS) implemented tiered reopening guidance between early June and late September, first reopening industries such as construction and manufacturing, followed by in-store retail, outdoor and indoor dining, and elementary schools, all at limited capacity 4. Following the introduction of these policies, the daily reported new cases in NYC declined to fewer than 700 per day in early June, down from over 10,000 cases per day at the peak of the epidemic in April 2020. Facial mask-wearing in public became mandatory in mid-April 3. Two weeks after the first case was reported in NYC, Governor Cuomo declared stay-at-home restrictions that included banning large gatherings and closing schools and non-essential businesses 1, 2. In March 2020, New York City (NYC) became the epicenter of the COVID-19 epidemic, accounting for more than one-third of the total confirmed cases in the US. High levels of adherence to social distancing and mask-wearing could have attributed to avoiding recurrent surges without reinstatement of stay-at-home restrictions. With low adherence to mask-wearing and social distancing, reinstatement of stay-at-home restrictions in NYC was inevitable. In threshold analyses, avoiding reinstatement of stay-at-home restrictions required a minimum of 60% adherence to mask-wearing at 50% adherence to social distancing. At moderate to high levels of adherence to mask-wearing without social distancing, NYC would have needed to implement stay-at-home restrictions. At a low (50%) level of adherence to mask-wearing, NYC would have needed to implement stay-at-home restrictions between 8% and 32% of the time depending on individual adherence to social distancing. NYC would have stayed fully open for 26% of the time until May 31, 2021, alternating reinstatement and relaxation of stay-at-home restrictions in four cycles. Without social distancing and mask-wearing, simulated relaxation of stay-at-home restrictions led to epidemic resurgence and necessary reinstatement of stay-at-home restrictions within 42 days. We assumed that the relaxation of stay-at-home policies would occur in the context of adaptive reopening, where a new hospitalization rate of ≥ 2 per 100,000 residents would trigger reinstatement of stay-at-home restrictions while a new hospitalization rate of ≤ 0.8 per 100,000 residents would trigger relaxation of stay-at-home restrictions. We projected daily new infections and hospitalizations up to under the different levels of adherence to social distancing and mask-wearing after relaxation of stay-at-home restrictions. The model was calibrated to hospitalizations, ICU admissions, and COVID-attributable deaths over March–July 2020 after accounting for the distribution of age and chronic health conditions in NYC. We applied a stochastic discrete time-series model to simulate community transmission and household secondary transmission in NYC. We projected the impact of individuals’ adherence to social distancing and mask-wearing on the duration, frequency, and recurrence of stay-at-home restrictions in NYC. Relaxation of these restrictions was desirable for resuming economic and social activities, but could only occur in conjunction with measures to mitigate the expected resurgence of new infections, in particular social distancing and mask-wearing. Stay-at-home restrictions such as closure of non-essential businesses were effective at reducing SARS-CoV-2 transmission in New York City (NYC) in the spring of 2020.
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