Recommended composition of influenza virus vaccines for use in the 2017- 2018 northern hemisphere influenza season
Recommended composition of influenza virus vaccines for use in the 2017-
2018 northern hemisphere influenza season
March 2017
Recommended composition of influenza virus vaccines for use in the 2017-2018
northern hemisphere influenza season
Influenza A(H3N2) viruses predominated in most countries, with low levels of A(H1N1)pdm09 and
influenza B viruses also circulating during the period September 2016 – February 2017.
Influenza A(H1N1)pdm09 viruses were antigenically indistinguishable by post-infection ferret
antisera raised against current vaccine viruses A/California/7/2009 and A/Michigan/45/2015.
However, representative circulating viruses were poorly inhibited by some post-vaccination adult
human serum pools.
Influenza A(H3N2) viruses were associated with outbreaks in many countries. The majority of recent
viruses were antigenically related to cell culture-propagated 3C.2a A/Hong Kong/4801/2014-like
viruses. A(H3N2) viruses within the 3C.2a clade have become genetically diverse, although they
remain antigenically similar. The majority of recently circulating A(H3N2) viruses belong to subclade
3C.2a1.
Influenza B viruses of the B/Victoria/2/87 and the B/Yamagata/16/88 lineages co-circulated at
similar levels in some regions, but in many countries in South America, Asia and Eastern Europe,
B/Victoria/2/87 lineage viruses were predominant. Most B/Victoria/2/87 lineage viruses were
antigenically and genetically closely related to B/Brisbane/60/2008 and B/Texas/2/2013. The majority
of recent B/Yamagata/16/88 lineage viruses were antigenically and genetically closely related to
B/Phuket/3073/2013.
It is recommended that trivalent vaccines for use in the 2017-2018 northern hemisphere
influenza season contain the following:
– an A/Michigan/45/2015 (H1N1)pdm09-like virus;
– an A/Hong Kong/4801/2014 (H3N2)-like virus; and
– a B/Brisbane/60/2008-like virus.
It is recommended that quadrivalent vaccines containing two influenza B viruses contain the
above three viruses and a B/Phuket/3073/2013-like virus.
Lists of egg- or cell culture-propagated candidate vaccine viruses (CVVs) suitable for use in human
vaccine production are available on the WHO website3
. A list of reagents for vaccine standardisation,
including those for this recommendation, can also be found on the WHO website. CVVs for zoonotic
influenza viruses are listed on the same website.
The World Health Organization (WHO) convenes technical consultations1 in February/March and
September each year to recommend viruses for inclusion in influenza vaccines2 for the northern and
southern hemisphere influenza seasons, respectively. This recommendation relates to the influenza
vaccines for use in the forthcoming northern hemisphere 2017-2018 influenza season. A
recommendation will be made in September 2017 relating to vaccines that will be used for the
southern hemisphere 2018 influenza season. For countries in tropical and subtropical regions,
epidemiological considerations influence which recommendation (northern hemisphere or southern
hemisphere) individual national and regional authorities consider appropriate.
Seasonal influenza activity, September 2016 – February 2017
Between September 2016 and February 2017 influenza activity was reported in Africa, the Americas,
Asia, Europe and Oceania. In general, activity was higher compared with the same period last year. In
the southern hemisphere, influenza activity was low in most countries, however, regional outbreaks
continued in South Africa during September and in Australia during September and October. In the
northern hemisphere, influenza activity began in Asia and Europe in October-November and had
increased in most countries by December. In many countries with tropical and subtropical climates,
influenza circulated during the entire reporting period.
Influenza A(H1N1)pdm09 viruses circulated at very low levels with a few exceptions. Influenza
A(H3N2) viruses were dominant in most countries and regional and widespread outbreaks were
reported in Asia, Europe, and North America. Influenza B viruses circulated at low levels in most
countries throughout the period while regional outbreaks were reported in Asia, western Africa and
the United States of America
