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Assessing Direct and Spillover Effects of Intervention Packages in Network-Randomized Studies.

ABSTRACT: Intervention packages may result in a greater public health impact than single interventions. Understanding the separate impact of each component in the overall package effectiveness can improve intervention delivery. We adapted an approach to evaluate the effects of a time-varying intervention package in a network-randomized study. In some network-randomized studies, only a subset of participants in exposed networks receive the intervention themselves. The spillover effect contrasts average potential outcomes if a person was not exposed themselves under intervention in the network versus no intervention in a control network. We estimated effects of components of the intervention package in HIV Prevention Trials Network 037, a Phase III network-randomized HIV prevention trial among people who inject drugs and their risk networks using Marginal Structural Models to adjust for time-varying confounding. The index participant in an intervention network received a peer education intervention initially at baseline, then boosters at 6 and 12 months. All participants were followed to ascertain HIV risk behaviors. There were 560 participants with at least one follow-up visit, 48% of whom were randomized to the intervention, and 1,598 participant-visits were observed. The spillover effect of the boosters in the presence of initial peer education training was a 39% rate reduction (Rate Ratio = 0.61; 95% confidence interval= 0.43, 0.87). These methods will be useful to evaluate intervention packages in studies with network features.

SUBMITTER: Buchanan AL

PROVIDER: S-EPMC10863001 | biostudies-literature | 2024 Feb

REPOSITORIES: biostudies-literature

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Assessing Direct and Spillover Effects of Intervention Packages in Network-Randomized Studies.

Buchanan Ashley L AL Hernández-Ramírez Raúl Ulises RU Lok Judith J JJ Vermund Sten H SH Friedman Samuel R SR Forastiere Laura L Spiegelman Donna D

medRxiv : the preprint server for health sciences 20240201

Intervention packages may result in a greater public health impact than single interventions. Understanding the separate impact of each component in the overall package effectiveness can improve intervention delivery. We adapted an approach to evaluate the effects of a time-varying intervention package in a network-randomized study. In some network-randomized studies, only a subset of participants in exposed networks receive the intervention themselves. The spillover effect contrasts average pot ...[more]

PMID: 38352598

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Project description:BackgroundDengue remains a global health challenge with limited treatment options, highlighting the need for effective vector control strategies. The introduction of Wolbachia pipientis into Aedes aegypti populations has shown success in reducing dengue transmission across global field trials. However, the spillover effectiveness of the technology on untreated areas is not well-known. This study estimates the spillover protective effectiveness (PE) of Wolbachia-mediated introgression on dengue.MethodsWe used the synthetic control method (SCM) under assumption of partial interference to evaluate the direct and spillover PEs of Wolbachia-mediated introgression in a long-running operational trial of the intervention in Malaysia. Synthetic controls (SCs), which comprise of a weighted sum of non-spillover controls, were constructed for each directly-treated and spillover site in the pre-intervention period to account for historical imbalances in dengue risk and risk trajectories. SCs were compared to directly/spillover-treated sites to estimate the impact of Wolbachia-introgression on dengue incidence across each site, calendar year and intervention time. Robustness checks, including visual inspections, root-mean-square error (RMSE) calculations, in-space and in-time placebo checks, and permutation tests, were used to inspect the model's ability in attributing dengue incidence reductions to the Wolbachia interventions.FindingsThe direct and spillover PEs of Wolbachia on dengue incidence were expressed as a percentage reduction of dengue incidence, or the absolute case reductions, by comparing SCs to actual intervention/spillover sites. Findings indicate a direct reduction in dengue incidence by 64.35% (95% CI: 63.50-66.71, p < 0.05 using permutation tests) in directly treated areas, corresponding to 1802 (95% CI: 1768-1932) cases averted. Meanwhile, spillover effects contributed to a 37.69% (95% CI: 36.45-38.49, p < 0.05) reduction in adjacent non-intervention areas, accounting for 115 (95% CI: 104-132) absolute cases averted. Tracking PEs by intervention time revealed a dose-response relationship, where PEs increased concomitantly with Wolbachia frequency. Model checks confirmed the robustness of these results, and ascertained that these PEs were not an artefact of poor control selection, pre-trends in dengue incidence or poor predictive ability of the fitted SCs.InterpretationWolbachia-introgression effectively diminished dengue incidence in directly-treated and surrounding spillover regions. This dual effectiveness highlights the potential of Wolbachia-infected mosquitoes as a sustainable, cost-effective strategy against dengue.FundingThis research is hosted by CNRS@CREATE and supported by the National Research Foundation, Prime Minister's Office, Singapore, under its Campus for Research Excellence and Technological Enterprise (CREATE) program, and is funded by the Lee Kong Chian School of Medicine-Ministry of Education Start-Up Grant. The original Hoffmann et al. (2024) study was funded by the Wellcome Trust Awards 226166, 108508, 202888 and the Ministry of Health Malaysia NMRR-16-297-28898.

Dataset Information

Assessing Direct and Spillover Effects of Intervention Packages in Network-Randomized Studies.

Publications

Assessing Direct and Spillover Effects of Intervention Packages in Network-Randomized Studies.

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