Influenza cost and cost-effectiveness studies globally--a review.

Every year, approximately 10-20% of the world's population is infected with influenza viruses, resulting in a significant number of outpatient and hospital visits and substantial economic burden both on health care systems and society. With recently updated WHO recommendations on influenza vaccination and broadening vaccine production, policy makers in middle- and low-income countries will need data on the cost of influenza disease and the cost effectiveness of vaccination. We reviewed the published literature to summarize estimates of cost and cost-effectiveness of influenza vaccination. We searched PUBMED (MEDLINE), EMBASE, WEB of KNOWLEDGE, and IGOOGLE using the key words 'influenza', 'economic cost', 'cost effectiveness', and 'economic burden'. We identified 140 studies which estimated either cost associated with seasonal influenza or cost effectiveness/cost-benefit of influenza vaccination. 118 of these studies were conducted in World Bank-defined high income, 22 in upper-middle income, and no studies in low and lower-middle income countries. The per capita cost of a case of influenza illness ranged from $30 to $64. 22 studies reported that influenza vaccination was cost-saving; reported cost-effectiveness ratios were $10,000/outcome in 13 studies, $10,000 to $50,000 in 13 studies, and ≥$50,000 in 3 studies. There were no studies from low income countries and few studies among pregnant women. Substantial differences in methodology limited the generalization of results. Decision makers in lower income countries lack economic data to support influenza vaccine policy decisions, especially of pregnant women. Standardized cost-effectiveness studies of influenza vaccination of WHO-recommended risk groups' methods are urgently needed.