The periodic replacement of virus strains contained in influenza vaccine is necessary because of the constant evolution of influenza viruses, which can change their antigenic and genetic characteristics. The World Health Organization (WHO) recommends the following influenza vaccine composition information.

Northern Hemisphere 2018-2019

WHO recommends 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.

More Information
WHO. (February 2018) Recommended composition of influenza virus vaccines for use in the 2018-2019 northern hemisphere influenza season - full report

WHO. (February 2018) Questions and Answers
Recommended composition of influenza virus vaccines for use in the 2018-2019 northern hemisphere influenza season and development of candidate vaccine viruses for pandemic preparedness

Southern Hemisphere 2018


WHO recommends that trivalent vaccines for use in the 2018 southern 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; and
•    a B/Phuket/3073/2013-like virus.

It is recommended that quadrivalent vaccines containing two influenza B viruses contain the above three viruses and a B/Brisbane/60/2008-like virus.

More Information
WHO. (September 2017) Recommended composition of influenza virus vaccines for use in the 2018 southern hemisphere influenza season - full report

WHO. (September 2017) Questions and Answers. Recommended composition of influenza virus vaccines for use in the southern hemisphere 2018 influenza season and development of candidate vaccine viruses for pandemic preparedness

(Updated 1 March 2018)