Abstract
The constantly changing pattern in the dominance of viral strains and their evolving subclades during the seasons substantially influences influenza vaccine effectiveness (IVE). In order to further substantiate the importance of detailed data of genetic virus characterization for IVE estimates during the seasons, we performed influenza virus type and subtype specific IVE estimates. IVE estimates were assessed using a test-negative case-control design, in the context of the intraseasonal changes of the heterogeneous mix of circulating influenza virus strains for three influenza seasons (2016/17 to 2018/19) in Austria. Adjusted overall IVE over the three seasons 2016/17, 2017/18, and 2018/19 were −26, 39, and 63%, respectively. In accordance with the changing pattern of the circulating strains a broad range of overall and subtype specific IVEs was obtained: A(H3N2) specific IVE ranged between −26% for season 2016/17 to 58% in season 2018/19, A(H1N1)pdm09 specific IVE was 25% for the season 2017/18 and 65% for the season 2018/19 and Influenza B specific IVE for season 2017/18 was 45%. The results obtained in our study over the three seasons demonstrate the increasingly complex dynamic of the ever changing genetic pattern of the circulating influenza viruses and their influence on IVE estimates. This emphasizes the importance of detailed genetic virus surveillance for reliable IVE estimates.
Highlights
Each year, influenza epidemics infect about 5–10% of adults and 10–20% of children
Annual influenza virus surveillance is performed from October through April and is based on sentinel physicians forming part of the Diagnostic Influenza Network Austria (DINOE), who collect nasopharyngeal swabs from patients presenting with influenza like illness as defined by the ECDC [7]
This paper presents data obtained by the Austrian sentinel surveillance system on the evolution of influenza viruses during the seasons 2016/17 to 2018/19 and the impact of genetic drift on influenza influenza vaccine effectiveness (IVE)
Summary
Influenza epidemics infect about 5–10% of adults and 10–20% of children. The most effective way to prevent influenza virus infection and associated complications is by vaccination [2, 3]. Influenza viruses continually change over time through genetic and antigenic drift of their surface glycoproteins to escape virus. Influenza Virus Genetic Heterogeneity and IVE neutralization by immune response. The composition of the influenza vaccines has to be reconsidered annually and if required, revision is performed according to the most recent changes of the circulating strains [4]. Despite the yearly update and revaccination, the ability of the vaccine to prevent influenza virus infection in the general population varies each year [2]
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