BackgroundVashon, WA is a rural community at risk from COVID-19 due to advanced age and limited access to acute care. Medical Reserve Corps are a national network of 800 volunteer healthcare organizations that have contributed to the pandemic response in many communities. Here we evaluate the effectiveness of the Vashon Medical Reserve Corp’s (VMRC) volunteer, community-based COVID-19 response program that integrated public engagement, SARS-CoV2 testing, contact tracing, vaccination and material support in reducing COVID-19 transmission and severe disease.MethodsThis observational cross-sectional study compares cumulative COVID-19 case, hospitalization and death rates on Vashon with other King County zip codes and the county at large from February 2020 through November 2021. We developed multiple linear regression models of COVID-19 rates using metrics of age, race/ethnicity, wealth and educational attainment across King County zip codes. Effectiveness of contact tracing was evaluated by timeliness and success of case investigations, and identification and testing of named contacts. Vaccination effectiveness was estimated by comparing time to reach vaccination milestones. We examined vehicle traffic on Vashon ferries and King County highways to understand whether reduced mobility contributed to Vashon’s reduced COVID-19 rates.ResultsVashon’s cumulative COVID-19 case rate was 29% that of King County overall and was lower across all age groups and races/ethnicities (both p<.01). A multiple linear regression model showed Vashon to be a significant outlier among King County zip codes with an observed rate 38% of predicted (p<.05), the lowest of any King County zip code. Vashon’s observed COVID-19 hospitalization and death rates were 22% and 32% of those predicted by parallel regression models. Hence, Vashon’s demographics do not explain its reduced COVID rates. Traffic reductions on King County highways and Vashon ferries were nearly identical throughout the study period suggesting altered mobility also does not explain Vashon’s low COVID-19 rates. Effectiveness of VMRC’s COVID-19 response program was demonstrated by 1) highly effective contact tracing that rapidly interviewed 93% of cases and subsequently tested 96% of named contacts, and 2) attainment of vaccination milestones 1-4 months earlier than comparable King County zip codes (p<.01).ConclusionVMRC’s volunteer, COVID-19 response program was associated with significantly fewer COVID-19 cases than predicted from its demographics. VMRC’s contact tracing and vaccination efforts were highly successful and likely contributed to reduced COVID-19 rates. The VMRC experience suggests that a decentralized community-based public health program can be highly effective in implementing epidemic control strategies when focused on an at-risk community. We suggest that MRCs can be particularly effective in extending the reach of county public health departments and should be included in ongoing pandemic planning.

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 < .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 < .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 < .001). Including vaccination rates in the model reduced the effect of remote geography to -41 cases/K (p < .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<0.001). VMRC’s public health interventions were associated with a 30% lower case rate (p<0.001) and 55% lower hospitalization rate (p = 0.056) than South Whidbey. Conclusions 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.