Predictive value of IHR surveillance (C.5) and laboratory (C.2) capacities for national measles incidence: A 2011–2023 panel analysis of 14 West African countries

Abstract Background: Despite sustained progress in immunization over the past decades, measles outbreaks persist in West Africa, suggesting gaps in disease detection and response systems. The International Health Regulations (IHR) State Party Self-Assessment Annual Reporting (SPAR) tool provides standardized indicators for laboratory capacity (C.2) and surveillance capacity (C.5). However, the extent to which these capacities, alongside vaccination coverage, influence measles incidence remains understudied. Methods: An ecological panel study was conducted using data from 14 West African countries (2011–2023). Measles case counts from the World Health Organization (WHO) Global Health Observatory were merged with laboratory (C.2) and surveillance (C.5) capacity indicators from the IHR SPAR tool. Measles-containing vaccine first-dose (MCV1) and second-dose (MCV2) coverage from WHO and the United Nations Children's Fund (UNICEF), and national-level covariates, including gross domestic product per capita, health expenditure, and population, were sourced from the World Bank. Descriptive analyses (means, standard deviations, correlations, scatterplots) were performed, followed by panel negative binomial and zero-inflated negative binomial regressions with interaction terms, adjusting for year fixed effects and population offset. Model diagnostics employed DHARMa simulations and variance inflation factor checks. Results: Higher SPAR surveillance capacity (C.5) was associated with increased reported measles incidence, moderated by first-dose vaccine coverage (MCV1; interaction p< 0.01). Laboratory capacity (C.2) was not significantly associated when considered jointly. GDP per capita and health expenditure were also not significant predictors. Zero-inflated models improved fit but did not alter substantive findings. Conclusions: Strengthening surveillance capacity enhances measles detection where vaccine coverage is suboptimal. Combining robust laboratory and surveillance systems with high vaccination uptake is vital for effective measles control in West Africa.