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The periodic replacement of viruses contained in influenza vaccines is necessary in order for the vaccines to be effective due to the constant evolving nature of influenza viruses, including those circulating and infecting humans. Twice annually, the World Health Organization (WH) organizes consultations with an advisory group of experts to analyze influenza virus surveillance data generated by the WHO Global Influenza Surveillance and Response System (GISRS), and issues recommendations on the composition of the influenza vaccines for the following influenza season. These recommendations are used by the national vaccine regulatory agencies and the pharmaceutical companies to develop, produce and license influenza vaccines.
WHO is recommending that quadrivalent vaccines for use in the 2018-2019 northern hemisphere influenza season contain the following:
an A/Michigan/45/2015 (H1N1)pdm09-like virus;
an A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus;
a B/Colorado/06/2017-like virus (B/Victoria/2/87 lineage); and
a B/Phuket/3073/2013-like virus (B/Yamagata/16/88 lineage).
It is recommended that the influenza B virus component of trivalent vaccines for use in the 2018-2019 northern hemisphere influenza season be a B/Colorado/06/2017-like virus of the B/Victoria/2/87-lineage.