How the COVID-19 pandemic and cost-of-living crisis shaped reach and engagement in the ECAIL trial targeting socially disadvantaged families: an interdisciplinary implementation study

Background: The ECAIL trial, launched in 2017, targets hard-to-reach families and evaluates a multicomponent childhood obesity prevention intervention. At a maternity hospital in Lille, France, healthcare providers screened pregnant women experiencing social vulnerability, and dietitians delivered a home-based intervention until age 2. The COVID-19 pandemic led to a six-month suspension in 2020. This study compared eligibility and participation before the pandemic and after resumption, and examined how the pandemic and subsequent cost-of-living crisis shaped implementation and reach. Methods: We analyzed 5,744 eligibility questionnaires distributed at the maternity ward. Inclusion criteria included [≥]1 indicator of social vulnerability (e.g., socioeconomic disadvantage, precarious housing, or social isolation). To capture implementation experiences, a psychosocial researcher conducted a focus group with six dietitians delivering the intervention; it was recorded, transcribed, and analyzed thematically focusing on reach, acceptability, and adaptation. Results: Eligibility increased from 29.7% (n=955) prepandemic to 33.6% (n=849) after resumption, while the distribution of vulnerability criteriaremainedsimilar across periods:78.3% received social/medical benefits; employment was not the main source of household income for 58.7%; 24.4% experienced financial hardship; 14.7% reported social isolation; 6.0% lived in precarious housing; and 19.0% had three or more vulnerabilities. Participation among eligible women remained stable (24.6%; n=443). Qualitative findings indicated dietitians satisfaction and participants enthusiasm for the resumption of home visits, particularly in addressing social isolation. After resumption, the introduction of a pre-visit COVID-19 questionnaire reduced missed appointments. Converging qualitative and quantitative findings indicated sustained, and in some cases strengthened, provider engagement despite pandemic-related strain on hospital services. Conclusions: This study shows that a complex intervention can maintain reach and acceptability through adaptive implementation under major contextual disruptions.The rapid resumption of home-based services emerged as a robust strategy for engaging and retaining socially disadvantaged families, highlighting the importance of flexible, context-sensitive approaches during social and economic crises.