US healthcare costs attributable to type A and type B influenza

ABSTRACT

While the overall healthcare burden of seasonal influenza in the United States (US) has been well characterized, the proportion of influenza burden attributable to type A and type B illness warrants further elucidation. The aim of this study was to estimate numbers of healthcare encounters and healthcare costs attributable to influenza viral strains A and B in the US during the 2001/2002 – 2008/2009 seasons. Healthcare encounters and costs in the US during the 2001/2002 – 2008/2009 seasons for influenza type A and influenza type B were estimated separately and collectively, by season and age group, based on data from published literature and secondary sources for: rates of influenza-related encounters requiring formal healthcare, unit costs of influenza-related healthcare encounters, and estimates of population size. Across 8 seasons, projected annual numbers of influenza-related healthcare encounters ranged from 11.3–25.6 million, and healthcare costs, from $2.0–$5.8 billion. While the majority of influenza illness was attributable to type A strains, type B strains accounted for 37% of healthcare costs across all seasons, and as much as 66% in a single season. The outpatient burden of type B disease was considerable among persons aged 18–64 y while the hospital cost burden was highest in young children. Influenza viral strain B was associated with considerable health system burden each year during the period of interest. Increasing influenza vaccine coverage, especially with the recently approved quadrivalent products including an additional type B strain, could potentially reduce overall annual influenza burden in the US.

KEYWORDS:

• burden
• healthcare costs
• influenza
• influenza A virus
• influenza B virus
• vaccine

Abbreviations

CI	=	confidence interval
CPI	=	consumer price index
DSA	=	deterministic sensitivity analyses
ED	=	emergency department
LOS	=	length of stay
MEPS-HC	=	Household Component of the Medical Expenditure Panel Survey
NOS	=	not otherwise specified
PSA	=	probabilistic sensitivity analyses
US	=	United States

Disclosure of potential conflicts of interest

DW is employed by PAI, which received funding for this research from the GSK group of companies. SS was used by PAI during the conduct of this analysis. SY was employed by the GSK group of companies at the time of the study conduct and during the development of the manuscript and is currently employed by CSL Behring. SY also reports holding of shares in the GSK group of companies and CSL Behring as part of his employee remuneration.

Acknowledgments

We thank Jenny Andersson Ph.D. of CROMSOURCE Ltd. (UK) and Marie Cloes Ph.D. of Business and Decision Life Sciences (Belgium), both on behalf of GSK Vaccines, for editorial support, Ellen M. Dukes Ph.D. of PAI for writing support, and Aaron Moynahan of PAI for modeling support and Girishanthy Krishnarajah, former employee of GSK, for her contribution to the study.

Funding

Funding for this research was provided by GlaxoSmithKline LLC, US to Policy Analysis Inc. (PAI). GlaxoSmithKline Biologicals SA was involved in all stages of the study conduct and analysis. GlaxoSmithKline Biologicals SA also funded all costs associated with the development and the publishing of the present manuscript (GSK study identifier HO-13–12299).

Authors' contributions

Authorship was designated based on the guidelines promulgated by the International Committee of Medical Journal Editors (2004). All persons who met criteria for authorship are listed as authors on the title page. The contribution of each of these individuals to this study was as follows: conception and supervision (SY and DW), development of design (all authors), conduct of analyses (SS and DW), interpretation of results (all authors), and preparation/review of manuscript (all authors). All authors have read and approved the final version of the manuscript. The study sponsor reviewed the study research plan and study manuscript; all final analytic decisions were made by study investigators.