Phylogenetic analysis of human influenza A/H3N2 viruses isolated in 2015 in Germany indicates significant genetic divergence from vaccine strains

Arch Virol. 2016 Jun;161(6):1505-15. doi: 10.1007/s00705-016-2815-x. Epub 2016 Mar 14.


Infections by H3N2-type influenza A viruses (IAV) resulted in significant numbers of hospitalization in several countries in 2014-2015, causing disease also in vaccinated individuals and, in some cases, fatal outcomes. In this study, sequence analysis of H3N2 viruses isolated in Germany from 1998 to 2015, including eleven H3N2 isolates collected early in 2015, was performed. Compared to the vaccine strain A/Texas/50/2012 (H3N2), the 2015 strains from Germany showed up to 4.5 % sequence diversity in their HA1 protein, indicating substantial genetic drift. The data further suggest that two distinct phylogroups, 3C.2 and 3C.3, with 1.6-2.3 % and 0.3-2.4 % HA1 nucleotide and amino acid sequence diversity, respectively, co-circulated in Germany in the 2014/2015 season. Distinct glycosylation patterns and amino acid substitutions in the hemagglutinin and neuraminidase proteins were identified, possibly contributing to the unusually high number of H3N2 infections in this season and providing important information for developing vaccines that are effective against both genotypes.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Child
  • Female
  • Genetic Drift
  • Genetic Variation
  • Germany / epidemiology
  • Glycosylation
  • Hemagglutinin Glycoproteins, Influenza Virus / chemistry
  • Hemagglutinin Glycoproteins, Influenza Virus / genetics
  • Humans
  • Influenza A Virus, H3N2 Subtype / classification
  • Influenza A Virus, H3N2 Subtype / genetics*
  • Influenza A Virus, H3N2 Subtype / isolation & purification
  • Influenza Vaccines / genetics
  • Influenza, Human / epidemiology
  • Influenza, Human / virology*
  • Male
  • Middle Aged
  • Models, Molecular
  • Phylogeny
  • Protein Structure, Tertiary
  • Selection, Genetic
  • Young Adult


  • Hemagglutinin Glycoproteins, Influenza Virus
  • Influenza Vaccines