Costs and cost-effectiveness of influenza illness and vaccination in low- and middle-income countries: A systematic review from 2012 to 2021

IntroductionHistorically, lack of data on cost-effectiveness of influenza vaccination has been identified as a barrier to vaccine use in low- and middle-income countries. We conducted a systematic review of economic evaluations describing (1) costs of influenza illness, (2) costs of influenza vaccination programs, and (3) vaccination cost-effectiveness from low- and middle-income countries to assess if gaps persist. MethodsWe performed a systematic search in Medline, Embase, Cochrane Library, CINAHL, and Scopus using a combination of the following key words: "influenza" AND "cost" OR "economic." The search included studies with publication years 2012 through 2021. We abstracted general study characteristics and data specific to each of the three areas of review. ResultsOf 50 included studies, 24 presented data on cost-effectiveness, 23 on cost-of-illness, and four on program costs. Represented countries were classified as upper-middle income (UMIC; n=11), lower-middle income (LMIC; n=7), and low-income (LIC; n=3). The most evaluated target groups were children (n=26 studies), older adults (n=16), and persons with chronic medical conditions (n=12); fewer studies evaluated pregnant persons (n=8), healthcare workers (n=4), and persons in congregate living settings (n=1). Costs-of-illness were generally higher in UMICs than in LMICs/LICs; however, the highest total costs, as a percent of gross domestic product and national health expenditure, were reported from an LIC. Among studies that evaluated the cost-effectiveness of influenza vaccine introduction, most (83%) interpreted at least one scenario per target group as either cost-effective or cost-saving, based on thresholds designated in the study. ConclusionsContinued evaluation of the economic burden of influenza illness and costs and cost-effectiveness of influenza vaccination, particularly in low-income countries and among underrepresented target groups (e.g., healthcare workers and pregnant persons), is needed; use of standardized methodology could facilitate pooling across settings. Robust, global economic data are critical to design and maintain sustainable influenza vaccination programs. Summary box What is already known on this topicPrior systematic reviews and surveys have demonstrated a need for economic data on influenza vaccination from low- and middle-income countries to inform program implementation and expansion. Standardized tools and guidance have become available in recent years to guide economic evaluations for influenza illness and vaccination in low-and middle-income countries. What this study addsThis article summarizes the literature on costs of influenza illness, costs of influenza vaccination programs, and vaccination cost-effectiveness from low- and middle-income country settings during 2012-2021. How this study might affect research, practice, or policyThe findings suggest value-for-money for influenza vaccination and increased interest in economic evaluations in recent years, but continued, standardized evaluation of costs and cost-effectiveness is needed, particularly from low-income countries and for underrepresented target groups.