Influenza: Can we cope better with the unpredictable?

Abstract

Seasonal influenza vaccines are unique because they are regularly reformulated and prepared in anticipation of the upcoming influenza season. Selection of vaccine strains occurs in advance of the influenza season, allowing time for vaccine production. Influenza viruses constantly evolve, and mismatches between vaccine strains and circulating strains have occurred in the past, impacting on vaccine effectiveness. The public health impact of a mismatch depends on multiple factors including strain virulence and transmission dynamics, pre-existing population immunity to the drift strain, and cross-reactivity induced by vaccination. Influenza vaccine effectiveness thus varies unpredictably from year to year, and may differ across European and northern American regions. Here we highlight the unpredictability associated with influenza virus circulation and present a comprehensive picture of circulating influenza strains in the northern hemisphere as compared to WHO recommendations for vaccine strains over the last 15 y. In years when vaccine mismatch occurs, such as the 2014–15 influenza season, public health agencies continue to recommend influenza vaccination as the preferred means by which to protect against influenza and influenza-associated complications. Research is on-going to optimise strain selection and vaccine composition to improve effectiveness.

KEYWORDS:

• circulating strains
• influenza
• vaccine-preventable diseases
• vaccines and immunisation

Abbreviations

EU	=	European Union
HA	=	haemagglutinin antigen
US	=	United States
VE	=	vaccine effectiveness
WHO	=	World Health Organization

Disclosure of potential conflicts of interest

Elisabeth Neumeier and Rafik Bekkat-Berkani are employees of the GSK group of companies and report ownership of stock options and/or restricted shares. Gaël Dos Santos reports he is working for GSK Vaccines, but is employed by Business & Decision Life Sciences.

Acknowledgments

The authors thank Bruce Innis and Riju Ray from GSK Vaccines for their critical review of the manuscript. The authors also thank Joanne Wolter (Independent medical writer, on behalf of GSK Vaccines) for providing writing services and Bruno Dumont (Business & Decision Life Sciences, on behalf of GSK Vaccines) for editorial assistance and manuscript coordination.

Authors' contributions

Gaël Dos Santos prepared the early draft of the communication. All authors participated in assembling and interpreting the data. All authors reviewed and approved the final manuscript.

Funding

GlaxoSmithKline Biologicals SA took in charge all costs associated with the development and publication of the present manuscript.