Influenza cost and cost-effectiveness studies globally – A review

Highlights

• There were no cost or cost-effectiveness of seasonal influenza vaccination studies from low income countries.

• Very few studies focused on pregnant women.

• Different methodologies across countries make extrapolation of results difficult.

• Most studies on children concluded that influenza vaccination was cost-saving.

• Indirect cost constituted a bigger portion of the cost of influenza in high income countries but not in middle income countries.

Abstract

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.

Introduction

Annually, influenza viruses are associated with a substantial disease burden throughout the world. Estimates derived from data in higher income countries suggest that seasonal influenza infections occur in approximately 10–20% of the world's population and may result in 3–5 million cases of severe illnesses and between 250,000 and 500,000 deaths worldwide [1]. Since the emergence of influenza H5N1 in 2003, increased investments into influenza surveillance and research has improved the quality and quantity of surveillance data globally especially from regions where previously no data had been available [2]. This accumulated data has helped to highlight the fact that influenza circulates globally, and that in some settings burden may be higher than experienced in higher income temperate regions due to a variety of factors that include lack of health care access, or specific co-morbidities such as HIV [3], [4]. The World Health Organization's Strategic Advisory Group of Experts (SAGE) has recently recommended that all countries should promote vaccination to a number of risk groups including young children, the elderly, and those with underlying conditions, with specific priority given to pregnant women in order to protect the mother and the future young infant [5].

Global increases in manufacturing capacity [6], both in number of doses and in diversity of countries producing vaccine, may allow for many countries that previously had little or no influenza vaccine experience to seriously consider its introduction into routine immunization programs [7]. For instance, the Pan American Health Organization (PAHO) has added influenza vaccine to its revolving fund of vaccines available at discount prices to countries in the PAHO region [7], and several countries including Brazil, Thailand and India are embarking on developing domestic seasonal influenza vaccine production capacity [8]. For many countries not yet able to afford broad introduction of vaccines, maternal influenza immunization to protect the mother and unborn child may be the first step and could possibly be subsidized in the future through GAVI mechanisms as for other new vaccines.

However, a primary driver of vaccine policy is the cost of the influenza vaccine, its delivery, and the economic impact of influenza. Countries with long standing influenza vaccination programs have conducted a variety of economic evaluation studies that assess the number of visits and admissions, quality adjusted life years lost, cost-of-illness, cost-effectiveness, cost–benefit analysis, and loss productivity, and these data point to substantial economic burden [10]. For example, one study estimated the annual cost of seasonal influenza in the United States between US$71 and 167 billion from the societal perspective [1].

As influenza vaccine manufacturing capacity increases globally and countries consider introduction of one or more of the SAGE recommended groups, cost and cost-effectiveness studies will be crucial in decision-making.

We conducted a systematic review of the literature (a) to assess current available data globally on cost and cost-effectiveness of influenza especially in target groups mentioned in the SAGE recommendations, (b) to determine trends and general patterns that can be used to extrapolate published data to countries considering vaccination and (c) to identify gaps in cost and cost-effectiveness analysis.