Malaria incidence before and after long-lasting insecticidal net distribution in four Zambian provinces, 2010-2021.

BACKGROUND

Zambia faces persistently high malaria morbidity and mortality rates, worsened by inadequate prevention and treatment resources, and high transmission. We aimed to assess the impact of three long-lasting insecticidal net (LLIN) distribution campaigns in four Zambian provinces from 2010 to 2021.

METHODS

We employed binomial regression and interrupted time series to analyze monthly malaria incidence across four provinces in Zambia (Eastern, Luapula, Northern and Northwestern) with a combined population of 5965257 within 1357 health facility catchment areas, utilizing data from the national Health Management Information System. We analyzed the association between LLIN distribution and trends in malaria incidence in terms of monthly cases confirmed by rapid diagnostic testing during January 2010-December 2021.

RESULTS

There was a significant reduction in malaria incidence rates following LLIN distribution. Temporal trends and seasonal patterns also influenced malaria transmission. Results showed a statistically significant decline in monthly malaria incidence rates following implementation of LLIN distribution, attributable to the immediate protective effects of nets; the binomial regression model showed up to 35% reduction in seasonally adjusted malaria incidence (rate ratio: 0.65, 95% CI 0.50 to 0.85; p=0.002).

CONCLUSIONS

Regular and timely replacement of nets is essential to maintain their protective benefits. This study highlights the key importance of LLINs for malaria control as part of wider strategies in Zambia and elsewhere.