Reach and engagement in the ECAIL trial targeting socially disadvantaged families across the COVID-19 pandemic and cost-of-living crisis: A mixed-methods implementation study

Background The ECAIL trial, launched in 2017, was designed to evaluate a multicomponent intervention for childhood obesity prevention among hard-to-reach families. 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 implementation and reach evolved across the pandemic and subsequent cost-of-living crisis. Methods Using a convergent mixed-methods design, we analyzed 5,744 eligibility questionnaires distributed at the maternity ward and conducted a focus group with six dieticians delivering the intervention to triangulate quantitative implementation indicators with qualitative implementation data. Inclusion criteria included ≥1 indicator of social vulnerability (e.g., socioeconomic disadvantage, precarious housing, or social isolation). The focus group was recorded, transcribed, and analyzed thematically focusing on reach, acceptability, and adaptation. Results Eligibility increased from 29.7% (n = 955) pre-pandemic to 33.6% (n = 849) after resumption, while the distribution of vulnerability criteria remained similar 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 was associated with fewer failed home visits. Integration of quantitative and qualitative findings indicated sustained, and in some cases strengthened, provider engagement despite pandemic-related strain on hospital services. Conclusions This study suggests 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 promising implementation strategy for engaging and retaining socially disadvantaged families, highlighting the importance of flexible, context-sensitive approaches during social and economic crises. Trial registration Clinicaltrials.gov NCT03003117; registration date: 21/12/2016; https://clinicaltrials.gov/study/NCT03003117 .