Prevalence of Influenza B/Yamagata Viruses From Season 2012/2013 to 2021/2022 in Italy as an Indication of a Potential Lineage Extinction

• Published in: Influenza and other respiratory viruses 2024-09, Vol.18 (9), p.e13359-n/a
• Main Authors: Marchi, Serena, Bruttini, Marco, Milano, Giovanna, Manini, Ilaria, Chironna, Maria, Pariani, Elena, Manenti, Alessandro, Kistner, Otfried, Montomoli, Emanuele, Temperton, Nigel, Trombetta, Claudia Maria
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Age groups; Aged; Amino acid sequence; Amino acids; Antibodies; Antibodies, Viral - blood; Antigens; Chi-square test; Child; Child, Preschool; Female; Gene sequencing; Genomic analysis; Health surveillance; Hemagglutination inhibition; Hemagglutination Inhibition Tests; Hemagglutinins; Humans; humoral immunity; Immunization; Immunoassay; Influenza; Influenza B; influenza B virus; Influenza B virus - classification; Influenza B virus - genetics; Influenza B virus - immunology; Influenza B virus - isolation & purification; Influenza Vaccines - immunology; Influenza, Human - epidemiology; Influenza, Human - virology; Italy - epidemiology; Male; Middle Aged; Original; Pandemics; Phylogeny; Prevalence; Proteins; Seasons; Sequence analysis; Serology; Vaccines; Viruses; Yamagata lineage; Young Adult
• ISSN: 1750-2640; 1750-2659; 1750-2659
• DOI: 10.1111/irv.13359

ABSTRACT Background Influenza B/Yamagata viruses exhibited weak antigenic selection in recent years, reducing their prevalence over time and requiring no update of the vaccine component since 2015. To date, no B/Yamagata viruses have been isolated or sequenced since March 2020. Methods The antibody prevalence against the current B/Yamagata vaccine strain in Italy was investigated: For each influenza season from 2012/2013 to 2021/2022, 100 human serum samples were tested by haemagglutination inhibition (HAI) assay against the vaccine strain B/Phuket/3073/2013. In addition, the sequences of 156 B/Yamagata strains isolated during the influenza surveillance activities were selected for analysis of the haemagglutinin genome segment. Results About 61.9% of the human samples showed HAI antibodies, and 21.7% had protective antibody levels. The prevalence of antibodies at protective levels in the seasons between the isolation of the strain and its inclusion in the vaccine was between 11% and 25%, with no significant changes observed in subsequent years. A significant increase was observed in the 2020/2021 season, in line with the increase in influenza vaccine uptake during the pandemic. Sequence analysis showed that from 2014/2015 season onward, all B/Yamagata strains circulating in Italy were closely related to the B/Phuket/2013 vaccine strain, showing only limited amino acid variation. Conclusions A consistent prevalence of antibodies to the current B/Yamagata vaccine strain in the general population was observed. The prolonged use of a well‐matched influenza vaccine and a low antigenic diversity of B/Yamagata viruses may have facilitated a strong reduction in B/Yamagata circulation, potentially contributing to the disappearance of this lineage.