A decade genetic diversity in Circulating influenza B virus in Iran (2010–2019): Divergence from WHO-recommended vaccine strains

Background. Data on the disease burden and circulation patterns of influenza B virus lineages for Iran are limited. Objective. This review aims to describe the pattern of influenza B occurrence in Iran, comparing it with the proposed vaccine strains and determining the match and mismatch with the prescribed vaccine annually. Methods. Various sources were used to retrieve information of the data; such as information from an online search of databases such as FluNet, GISAID, and NCBI. After extracting protein sequence records in GISAID, sequence alignment with vaccine strain and construction of a phylogenetic tree were performed. Subsequently, categories of the registered circulating strains were evaluated for matching with the vaccine strains. Results. Of the total registered influenza-positive samples, 20.21% were related to influenza B virus. The phylogenic tree was designed based on 43 samples registered in the GISAID database; 76.74 and 23.25% sequences were of Yamagata and Victoria lineages, respectively. The most prevalent influenza B virus strains circulating during the study years belonged to the Yamagata lineage. In general, the match of the influenza B virus predominant circulating strains with administrated vaccines was observed in Iran. However, a high level of mismatch between the vaccine strain and Iranian isolates was identified in 2016‒2017. Conclusion. The review of match and mismatch in influenza vaccine in order to improve the composition of the prescribed vaccine in each region is very important because the vaccine efficacy decreased when the strain included in vaccine did not match the circulating epidemic strain.