Freedom From Infection in Cabo Verde: Supporting Evidence-Based Decision-Making for Malaria Elimination

Abstract Background Cabo Verde was certified malaria-free in January 2024, yet remains at risk given continued importation and ecological receptivity across multiple islands. Quantifying how robust health systems are in preventing malaria reintroduction, and how sensitive elimination conclusions are to key definitional assumptions, can support programmatic decision-making to maintain absence of transmission. We aimed to estimate facility-level evidence for freedom from infection using the Freedom From Infection (FFI) framework, stress-test conclusions under different operational definitions of elimination, and compare classifications before versus after certification. Methods We extended and applied the FFI framework to jointly model latent malaria infections and the surveillance detection cascade. We combined 14 years of passive surveillance data from 25 facilities with health-facility capacity surveys and active surveillance to estimate the probability of freedom from infection (\(\:{P}^{FREE}\)). Robustness to critical elimination thresholds was assessed by varying both the population denominator (people per infection) and the \(\:{P}^{FREE}\) evidence cut-off, and by comparing classifications before versus after certification. Results Using a reference operational definition of elimination as fewer than one infection per 10,000 people and requiring at least 95% posterior confidence of being below that threshold, 18/25 facilities (72%) met the criterion in December 2024. Fewer facilities met elimination criteria under more stringent thresholds. Classifications were largely stable between pre- and post-certification periods, with no facilities improving and only a small number decreasing. Conclusions Maintaining strong surveillance system capacity is essential to sustain malaria elimination, particularly in settings with continued importation risk. The FFI framework provides a tool to quantify evidence for freedom from infection, stress-test elimination assumptions, and inform the likelihood of achieving and sustaining interruption of malaria transmission.