WHO reveals delayed pick for H3N2 flu vaccine strain

After waiting an extra month to decide on the H3N2 strain, World Health Organization (WHO) vaccine advisors finalized their recommendations on strains to include in the Northern Hemisphere 2019-20 flu vaccines. Their H3N2 recommendation—an A/Kansas/14/2017-like virus—reflects a change from the current Northern Hemisphere vaccine and is not a component of the Southern Hemisphere 2019 flu vaccines, either. New subclade rising sharply in US, elsewhere When making the announcement on the 2009 H1N1 and influenza B components at the end of their meeting in February, the experts noted increased numbers of genetically and antigenically diverse strains, with the number of clade 3C.3a viruses rising in several geographic regions. In its update today, the WHO said the proportion of viruses falling into that clade has increased substantially since November in several countries in western Europe, Israel, and especially the United States. H3N2 viruses pose an increasing challenge for experts picking the vaccine strains because of frequent changes...