WHO releases next season's influenza vaccine recommendations

The World Health Organization recommended on Thursday that two of the three strains in next season's influenza vaccine be changed for the Northern Hemisphere.

Influenza experts for the WHO called for changing the B and A/H3N2 components of the vaccine, while continuing to use the pandemic A/H1N1 2009 component. The change ends a couple of years of stability for the makeup of the vaccine, CIDRAP News reports.

While the current flu season has been quiet throughout the majority of the world, the recommendation shows that a significant amount of flu viruses recently circulating do not match up closely with the current vaccine.

For the 2012-13 season, the WHO recommends strains similar to the A/California/7/2009 H1N1 pdm09, the A/Victoria/361/2011 H3N2, replacing the A/Perth/16/2009, and the B/Wisconsin/1/2010, replacing the B/Brisbane/60/2008.

Experts from the WHO make North Hemisphere flu recommendations in February so that time can be allowed for the preparation of vaccine viruses and growing them in eggs. The Southern Hemisphere recommendation is typically made in October, CIDRAP News reports.

The strain changes are the first in the Northern Hemisphere vaccine since February 2010. While most of the isolates of circulating H1N1 strains have been similar to the vaccine strain, the H3N2 viruses have been distinguishable from the current vaccine strain. Influenza B viruses come in two lineages and the recommendation mark a switch from Victoria to Yamagata.