WHO issues recommendation on composition of influenza virus vaccines for northern hemisphere 2014-2015
Recommended composition of influenza virus vaccines for use in the 2014-2015 northern hemisphere influenza season
World Health Organization, Geneva, Switzerland, 21 February 2014:
The World Health Organization (WHO) has agreed on the recommended composition of the trivalent influenza vaccine for the season 2014-2015 as:
- an A/California/7/2009 (H1N1)pdm09-like virus;
- an A/Texas/50/2012 (H3N2)-like virus;
- a B/Massachusetts/2/2012-like virus (Yamagata lineage).
For quadrivalent vaccines containing two influenza B viruses the above three viruses and a B/Brisbane/60/2008-like virus (Victoria lineage) should be included.
All recommended vaccine viruses remain the same as the ones recommended for northern hemisphere season 2013-2014. Further antigenic and genetic characteristics of recent seasonal influenza viruses are described below.
Influenza A(H1N1)pdm09 viruses
The A(H1N1)pdm09 viruses remain antigenically homogeneous and closely related to the earlier vaccine virus A/California/7/2009 and therefore there is no change in the recommendation. The sequence analysis of the HA genes of A(H1N1)pdm09 viruses indicated that the viruses fell within several genetic groups which were antigenically indistinguishable.
Influenza A(H3N2) viruses
No major antigenic drift has been observed in the A(H3N2) viruses and therefore no change in the recommendation is made. The recently circulating viruses were well inhibited by ferret antisera raised against cell-propagated reference viruses such as A/Texas/50/2012 and A/Victoria/361/2011. The HA genes of recent A(H3N2) viruses fell into two main phylogenetic groups.
Influenza B viruses
The B/Yamagata/16/88 and the B/Victoria/2/87 lineage viruses have continued to co-circulate across the world with a predominance of the B/Yamagata lineage.
The majority of circulating viruses of the B/Yamagata/16/88 lineage were antigenically indistinguishable from the previous vaccine virus of the B/Yamagata/16/88 lineage (B/Massachusetts/2012), which has now also been recommended as a vaccine strain.
In addition, the majority of viruses of the B/Victoria/2/87 lineage were antigenically closely related to the earlier vaccine virus B/Brisbane/60/2008. That virus has now been recommended as a component of the quadrivalent vaccines.
