Changes in Malaria Burden and Preventive Intervention Coverage in Liberia: An Interrupted Time Series Analysis
##semicolon##
Malaria burden; malaria prevention; interrupted time series; mixed-effects modelling; routine surveillance; Liberia.##article.abstract##
Malaria remains a major public health challenge in Liberia despite continued efforts to control the disease. This study examined changes in malaria burden and preventive intervention coverage from January 2021 to December 2025, focusing on the period following January 2023. Monthly county-level surveillance data were obtained from Liberia’s Health Management Information System and analyzed using a longitudinal ecological design. Annual trends were summarized descriptively, followed by interrupted time series regression to assess changes after January 2023. A multivariable linear mixed-effects model examined the independent associations between preventive intervention coverage and malaria burden. Confirmed malaria cases fell from 742,092 in 2021 to 542,070 in 2023, before rising to 759,957 in 2025. Immediately after January 2023, malaria test positivity (β₂ = 3.67, p = 0.038), severe malaria (β₂ = 4.52, p < 0.001) and malaria-related deaths (β₂ = 2.87, p = 0.041) increased significantly. IPTp3 (β₂ = −9.10, p = 0.021) and IPTp3+ (β₂ = −7.72, p = 0.034) also declined immediately while LLIN coverage showed a significant decline in the post-interruption trend (β₃ = −4.12, p = 0.041). In the adjusted model, higher IPTp3 (β = −0.063, p = 0.001) and LLIN coverage (β = −0.052, p = 0.002) were associated with lower malaria burden. The study concludes that routine surveillance can help track malaria trends and program performance. Sustaining preventive interventions and using surveillance evidence in program planning may strengthen malaria control in Liberia.
##submission.citations##
Accrombessi, M., Yovo, E., Fievet, N., Hounkonnou, C. P. A., Mama, A., Sossou, D., Vianou, B., Massougbodji, A., Briand, V., Cot, M., & Cottrell, G. (2020). Suboptimal intermittent preventive treatment in pregnancy (IPTp) is associated with an increased risk of submicroscopic Plasmodium falciparum infection in pregnant women: A prospective cohort study in Benin. Clinical Infectious Diseases, 73(11), e3759–e3767. https://doi.org/10.1093/cid/ciaa1355.
Bernal, J. L., Cummins, S., & Gasparrini, A. (2017). Interrupted time series regression for the evaluation of public health interventions: A tutorial. International Journal of Epidemiology, 46(1), 348–355. https://doi.org/10.1093/ije/dyw098.
Bhatt, S., Weiss, D. J., Cameron, E., Bisanzio, D., Mappin, B., Dalrymple, U., Battle, K. E., Moyes, C. L., Henry, A., Eckhoff, P. A., Wenger, E. A., Briët, O., Penny, M. A., Smith, T. A., Bennett, A., Yukich, J., Eisele, T. P., Griffin, J. T., Fergus, C. A. and Gething, P. W. (2015). The effect of malaria control on Plasmodium falciparum in Africa between 2000 and 2015. Nature, 526(7572), 207–211. https://doi.org/10.1038/nature15535.
Global Fund to Fight AIDS, Tuberculosis and Malaria (2023). Results report 2023. https://www.theglobalfund.org/media/13263/corporate_2023resultsreport_report_en.pdf.
Hogan, A. B., Jewell, B. L., Sherrard-Smith, E., Vesga, J. F., Watson, O. J., Whittaker, C., Hamlet, A., Smith, J. A., Winskill, P., Verity, R., Baguelin, M., Lees, J. A., Whittles, L. K., Ainslie, K. E. C., Bhatt, S., Boonyasiri, A., Brazeau, N. F., Cattarino, L., Cooper, L. V., ... Hallett, T. B. (2020). Potential impact of the COVID-19 pandemic on HIV, tuberculosis, and malaria in low-income and middle-income countries: A modelling study. The Lancet Global Health, 8(9), e1132–e1141. https://doi.org/10.1016/S2214-109X(20)30288-6.
Kayentao, K., Garner, P., van Eijk, A. M., Naidoo, I., Roper, C., Mulokozi, A., MacArthur, J. R., Luntamo, M., Ashorn, P., Doumbo, O. K., & ter Kuile, F. O. (2013). Intermittent preventive therapy for malaria during pregnancy using 2 vs 3 or more doses of sulfadoxine-pyrimethamine and risk of low birth weight in Africa: Systematic review and meta-analysis. JAMA, 309(6), 594–604. https://doi.org/10.1001/jama.2012.216231.
Ministry of Health Liberi. (2022). National malaria strategic plan 2021–2025. Ministry of Health, Republic of Liberia.
Ministry of Health Liberia. (2023). Health management information system (HMIS) annual report. Ministry of Health, Republic of Liberia.
Sherrard-Smith, E., Hogan, A. B., Hamlet, A., Watson, O. J., Whittaker, C., Winskill, P., Ali, F., Mohammad, A. B., Uhomoibhi, P., Maikore, I., Ogbulafor, N., Nikau, J., Kont, M. D., Challenger, J. D., Verity, R., Lambert, B., Cairns, M., Rao, B., Baguelin, M., ... Churcher, T. S. (2020). The potential public health consequences of COVID-19 on malaria in Africa. Nature Medicine, 26(9), 1411–1416. https://doi.org/10.1038/s41591-020-1025-y.
Snow, R. W., Sartorius, B., Kyalo, D., Maina, J., Amratia, P., Mundia, C. W., Bejon, P., & Noor, A. M. (2017). The prevalence of Plasmodium falciparum in sub-Saharan Africa since 1900. Nature, 550(7677), 515–518. https://doi.org/10.1038/nature24059
Wagner, A. K., Soumerai, S. B., Zhang, F., & Ross-Degnan, D. (2002). Segmented regression analysis of interrupted time series studies in medication use research. Journal of Clinical Pharmacy and Therapeutics, 27(4), 299–309. https://doi.org/10.1046/j.1365-2710.2002.00430.x.
WHO (2017). Achieving and maintaining universal coverage with long-lasting insecticidal nets for malaria control. Global Malaria Program. https://www.who.int/publications/i/item/WHO-HTM-GMP-2017.20.
WHO (2023a). Liberia malaria country profile. https://www.who.int/publications/m/item/malaria-2023-lbr-country-profile.
WHO (2023b). World malaria report 2023. https://www.who.int/publications/i/item/9789240086173.
WHO (2024). World malaria report 2024. https://www.who.int/publications/i/item/9789240104440.
