Influenza: Did the vaccine work for 2012/2013?

For the 2012–2013 Influenza season, the recommendations for the influenza trivalent vaccine included A/California/7/2009 (H1N1)pdm09-like, A/Victoria/361/2011 (H3N2)-like and B/Wisconsin/1/2010-like (from the B/Yamagata lineage) viruses. Throughout the season, 99% of both the A(H1N1)pdm09 and A(H3N2) viruses characterized have been A/California/7/2009 (H1N1)pdm09-like and A/Victoria/361/2011 (H3N2)-like, suggesting a good match with the current seasonal vaccine.

[Foto: harvard.edu]

However, the situation was somewhat more complicated with the B viruses. The large majority of influenza B viruses detected globally were of the Yamagata lineage and nearly all of those were antigenically similar to the B/Wisconsin/1/2010-like virus contained in the trivalent seasonal vaccine.

A significant number of Victoria lineage viruses were also reported accounting for up to 30% of the B viruses in some countries.

The answer must be: the vaccine worked but only partially.

Source: WHO (pdf here)