Vaccine . Predominance of Influenza Virus A(H3N2) 3C.2a1b and A(H1N1)pdm09 6B.1A5A Genetic Subclades in the WHO European Region, 2018-2019

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Vaccine


. 2020 Jul 2;S0264-410X(20)30804-5.
doi: 10.1016/j.vaccine.2020.06.031. Online ahead of print.
Predominance of Influenza Virus A(H3N2) 3C.2a1b and A(H1N1)pdm09 6B.1A5A Genetic Subclades in the WHO European Region, 2018-2019


Angeliki Melidou ¹ , Olav Hungnes ² , Dmitriy Pereyaslov ³ , Cornelia Adlhoch ⁴ , Hannah Segaloff ³ , Emmanuel Robesyn ⁴ , Pasi Penttinen ⁴ , Sonja J Olsen ³ , European Region influenza surveillance network



Affiliations

• PMID: 32624252
• DOI: 10.1016/j.vaccine.2020.06.031

Abstract

Background: The 2018/2019 influenza season in the WHO European Region was dominated by influenza A (H1N1)pdm09 and (H3N2) viruses, with very few influenza B viruses detected.
Methods: Countries in the European Region reported virus characterization data to The European Surveillance System for weeks 40/2018 to 20/2019. These virus antigenic and genetic characterization and haemagglutinin (HA) sequence data were analysed to describe and assess circulating viruses relative to the 2018/2019 vaccine virus components for the northern hemisphere.
Results: Thirty countries reported 4776 viruses characterized genetically and 3311 viruses antigenically. All genetically characterized A(H1N1)pdm09 viruses fell in subclade 6B.1A, of which 90% carried the amino acid substitution S183P in the HA gene. Antigenic data indicated that circulating A(H1N1)pdm09 viruses were similar to the 2018/2019 vaccine virus. Genetic data showed that A(H3N2) viruses mostly fell in clade 3C.2a (75%) and 90% of which were subclade 3C.2a1b. A lower proportion fell in clade 3C.3a (23%) and were antigenically distinct from the vaccine virus. All B/Victoria viruses belonged to clade 1A; 30% carried a double amino acid deletion in HA and were genetically and antigenically similar to the vaccine virus component, while 55% carried a triple amino acid deletion or no deletion in HA; these were antigenically distinct from each other and from the vaccine component. All B/Yamagata viruses belonged to clade 3 and were antigenically similar to the virus component in the quadrivalent vaccine for 2018/2019.
Conclusions: A simultaneous circulation of genetically and antigenically diverse A(H3N2) and B/Victoria viruses was observed and represented a challenge to vaccine strain selection.

Keywords: Antigenic; Europe; Genetic; Influenza; Surveillance; Vaccine.