DOI: 10.7272/q6bk19m6
title: Interplay of demographics, geography and COVID-19 pandemic responses in the Puget Sound region: The Vashon, Washington Medical Reserve Corps experience

description: Background Rural U.S. communities are at risk from COVID-19 due to
 advanced age and limited access to acute care. Recognizing this, the
 Vashon Medical Reserve Corps (VMRC) in King County, Washington,
 implemented an all-volunteer, community-based COVID-19 response program.
  This program integrated public engagement, SARS-CoV-2 testing,
 contact tracing, vaccination, and material community support, and was
 associated with the lowest cumulative COVID-19 case rate in King County.
 This study aimed to investigate the contributions of demographics,
 geography and public health interventions to Vashon’s low COVID-19 rates.
 Methods This observational cross-sectional study compares cumulative
 COVID-19 rates and success of public health interventions from February
 2020 through November 2021 for Vashon Island with King County (including
 metropolitan Seattle) and Whidbey Island, located ~50 km north of Vashon.
 To evaluate the role of demography, we developed multiple linear
 regression models of COVID-19 rates using metrics of age, race/ethnicity,
 wealth and educational attainment across 77 King County zip codes. To
 investigate the role of remote geography we expanded the regression models
 to include North, Central and South Whidbey, similarly remote island
 communities with varying demographic features. To evaluate the
 effectiveness of VMRC’s community-based public health measures, we
 directly compared Vashon’s success of vaccination and contact tracing with
 that of King County and South Whidbey, the Whidbey community most similar
 to Vashon. Results Vashon’s cumulative COVID-19 case rate was 29% that of
 King County overall (22.2 vs 76.8 cases/K). A multiple linear regression
 model based on King County demographics found educational attainment to be
 a major correlate of COVID-19 rates, and Vashon’s cumulative case rate was
 just 38% of predicted (p&lt;.05), so demographics alone do not explain
 Vashon’s low COVID-19 case rate. Inclusion of Whidbey communities in the
 model identified a major effect of remote geography (-49 cases/K,
 p&lt;.001), such that observed COVID-19 rates for all remote
 communities fell within the model’s 95% prediction interval. VMRC’s
 vaccination effort was highly effective, reaching a vaccination rate of
 1500 doses/K four months before South Whidbey and King County and
 maintaining a cumulative vaccination rate 200 doses/K higher throughout
 the latter half of 2021 (p&lt;.001). Including vaccination rates in
 the model reduced the effect of remote geography to -41 cases/K
 (p&lt;.001). VMRC case investigation was also highly effective,
 interviewing 96% of referred cases in an average of 1.7 days compared with
 69% in 3.7 days for Washington Department of Health investigating South
 Whidbey cases and 80% in 3.4 days for Public Health–Seattle & King
 County (both p&lt;0.001). VMRC’s public health interventions were
 associated with a 30% lower case rate (p&lt;0.001) and 55% lower
 hospitalization rate (p=0.056) than South Whidbey. Conclusion While the
 overall magnitude of the pre-Omicron COVID-19 pandemic in rural and urban
 U.S. communities was similar, we show that island communities in the Puget
 Sound region were substantially protected from COVID-19 by their
 geography. We further show that a volunteer community-based COVID-19
 response program was highly effective in the Vashon community, augmenting
 the protective effect of geography. We suggest that Medical Reserve Corps
 should be an important element of future pandemic planning. 
description: The study period extended from the pandemic onset in February
 2020 through November 2021. Daily COVID-19 cases, hospitalizations, deaths
 and test numbers for King County as a whole and by zip code were
 downloaded from the King County COVID-19 dashboard (Feb 22, 2022 update). Population data for King County and Vashon are from the April 2020 US Census. Zip code level population data are the average of two zip code tabulation area estimates from the WA Office of Financial Management and Cubit (a commercial data vendor providing access to US Census information). The Asset Limited, Income Constrained, and Employed (ALICE) metric, a measure of the working poor, was obtained from United Way.