Australian Flu Season Bears Ill-Portents for US Flu Season

The Australian 2017 flu season (May-September) was unusually bad. A confluence of factors led to a higher incidence of hospital visits and a higher number of people infected than in previous flu seasons. Chief among these was an apparent failure of the current H3N2 vaccine to prevent viral infection. Given that this is the same vaccine strain as the H3N2 strain in the currently disseminated US flu vaccine, this means that the US flu season might be especially disruptive this year.
            H3N2 is an Influenza A virus, and this year it made up a plurality of the hospitalized cases of flu in Australia. It is estimated that the current vaccination for H3N2 was only 10% effective at reducing hospitalizations this year, despite moderate protection from the other two strains (protecting against Influenza B and H1N1). This failure of the H3N2 vaccine can likely be traced to problems in H3N2 candidate vaccine virus selection. H3N2 vaccine viruses tend to be highly mutable during production, leading to strains of the vaccine that drift away from the antigenic identity of the circulating virus.

-Cole Holderman
            Sources:

1.       Article in Eurosurveillance: Low interim influenza vaccine effectiveness, Australia, 1 May to 24 September, 2017: http://www.eurosurveillance.org/docserver/fulltext/eurosurveillance/22/43/eurosurv-22-43-1.pdf?expires=1513257892&id=id&accname=guest&checksum=A294D88E8787243FFE8D11612441F575

2.       Article in Shots by NPR: https://www.npr.org/sections/health-shots/2017/12/08/569379155/in-the-u-s-flu-season-could-be-unusually-harsh-this-year