# Geographical Variation in SARS-CoV-2 Transmission Potential in Massachusetts

## TL;DR

This study analyzed how SARS-CoV-2 spread differently across regions in Massachusetts from 2020 to 2022 and how nonpharmaceutical interventions affected transmission.

## Contribution

The study provides new insights into the regional effectiveness of early nonpharmaceutical interventions on SARS-CoV-2 transmission in Massachusetts.

## Key findings

- School closures and gathering restrictions in 2020 reduced the reproduction number (Rt) by 14.7% statewide.
- High-density areas like Boston saw a 16.9% reduction in Rt due to these interventions.
- Other NPIs like mask mandates and curfews did not significantly impact Rt.

## Abstract

Background/Objectives: This ecological study aimed to investigate changes in the time-varying reproduction number (Rt) of SARS-CoV-2 across six regions of Massachusetts from 2020 to 2022 and to evaluate the impact of various nonpharmaceutical interventions (NPIs) implemented in 2020 by examining associated changes in the Rt. Methods: COVID-19 incident case data from the Johns Hopkins University database were adjusted for reporting delays using deconvolution and for underreporting via a Poisson-distributed multiplier of 4. Negative and zero counts were corrected using imputation. Rt was estimated using R package EpiEstim (Version 2.2-4) with a 7-day sliding window from 2020 to 2022 and with non-overlapping time windows between policy changes in 2020. Results: From 2020 to 2022, Massachusetts experienced five COVID-19 surges, linked to the wild-type strain and emerging variants, with Rt exceeding 1 during each wave and stabilizing at or dropping below 1 during low-incidence phases. School closure and gathering restrictions, the first major intervention, were associated with a 14.7% statewide reduction in Rt (95% credible interval (CrI): −23.6%, −5.6%), with greater reductions in high-density areas such as Boston (−16.9%; 95% CrI: −26.9%, −7.5%). No statistically significant changes in Rt were found to be associated with other NPIs in 2020, including the mask mandate, reopening phases, travel restrictions and quarantine requirements, and curfews. Conclusions: Our findings highlight the different NPIs’ varying impacts on COVID-19 transmission dynamics across regions in Massachusetts in 2020 and underscore the importance of early interventions for future pandemic preparedness.