Description:
<jats:title>Abstract</jats:title>
<jats:sec id="S1935789322002129_as1">
<jats:title>Introduction:</jats:title>
<jats:p>We aimed to examine how public health policies influenced the dynamics of coronavirus disease 2019 (COVID-19) time-varying reproductive number (<jats:italic>R</jats:italic><jats:sub>
<jats:italic>t</jats:italic>
</jats:sub>) in South Carolina from February 26, 2020, to January 1, 2021.</jats:p>
</jats:sec>
<jats:sec id="S1935789322002129_as2">
<jats:title>Methods:</jats:title>
<jats:p>COVID-19 case series (March 6, 2020, to January 10, 2021) were shifted by 9 d to approximate the infection date. We analyzed the effects of state and county policies on <jats:italic>R</jats:italic><jats:sub>
<jats:italic>t</jats:italic>
</jats:sub> using EpiEstim. We performed linear regression to evaluate if per-capita cumulative case count varies across counties with different population size.</jats:p>
</jats:sec>
<jats:sec id="S1935789322002129_as3">
<jats:title>Results:</jats:title>
<jats:p><jats:italic>R</jats:italic><jats:sub>
<jats:italic>t</jats:italic>
</jats:sub> shifted from 2-3 in March to <1 during April and May. <jats:italic>R</jats:italic><jats:sub>
<jats:italic>t</jats:italic>
</jats:sub> rose over the summer and stayed between 1.4 and 0.7. The introduction of statewide mask mandates was associated with a decline in <jats:italic>R</jats:italic><jats:sub>
<jats:italic>t</jats:italic>
</jats:sub> (−15.3%; 95% CrI, −13.6%, −16.8%), and school re-opening, an increase by 12.3% (95% CrI, 10.1%, 14.4%). Less densely populated counties had higher attack rates (<jats:italic>P</jats:italic> < 0.0001).</jats:p>
</jats:sec>
<jats:sec id="S1935789322002129_as4">
<jats:title>Conclusions:</jats:title>
<jats:p>The <jats:italic>R</jats:italic><jats:sub>
<jats:italic>t</jats:italic>
</jats:sub> dynamics over time indicated that public health interventions substantially slowed COVID-19 transmission in South Carolina, while their relaxation may have promoted further transmission. Policies encouraging people to stay home, such as closing nonessential businesses, were associated with <jats:italic>R</jats:italic><jats:sub>
<jats:italic>t</jats:italic>
</jats:sub> reduction, while policies that encouraged more movement, such as re-opening schools, were associated with <jats:italic>R</jats:italic><jats:sub>
<jats:italic>t</jats:italic>
</jats:sub> increase.</jats:p>
</jats:sec>