A Methodological Framework for Assessing Cold Chain Integrity and Measles Vaccine Seroconversion in Remote Angolan Health Facilities

This methodology article presents a novel, integrated framework for assess the integrity of the vaccine cold chain and its direct association with measles vaccine seroconversion rates in remote Angolan health facilities. The persistent challenge of suboptimal vaccine efficacy in such settings, despite high reported coverage, necessitates robust tools to investigate the often-suspected, yet poorly quantified, role of cold chain failures. The proposed mixed-methods, longitudinal design, to be implemented over an 18-month period from 2025, systematically combines quantitative and qualitative data collection. It employs continuous temperature monitoring with digital data loggers across the supply chain, paired with serological testing of infant cohorts to determine immunogenicity. Concurrently, structured interviews and observational checklists will capture contextual operational realities. The core methodological innovation is the analytical integration of these datasets to model the probabilistic relationship between specific cold chain exposure variables and seroconversion failure. This approach moves beyond simple compliance audits to establish causative links. The framework is designed for implementation by national public health teams, providing a critical evidence base for targeted cold chain investments and policy revisions. By offering a replicable model for vaccine programme evaluation, this methodology directly supports the African Union's Agenda 2026 goal for health security, aiming to strengthen immunisation systems and reduce vaccine-preventable mortality in logistically challenging environments.