Last winter the U.S. experienced a vicious flu season, with the Centers for Disease Control and Prevention (CDC) reporting new highs for pediatric mortality and hospitalizations of seniors. Now preparations for 2013-2014 are under way, with companies preparing the first quadrivalent shots.
The value of immunizing against an additional influenza B strain is apparent looking at data from last year's flu season. The CDC collected data on 876 influenza B viruses, of which two-thirds were part of the B/Yamagata lineage included in last year's trivalent vaccines. The remaining one-third of tested influenza B viruses belonged to the B/Victoria lineage. Last year's vaccines provided no protection against these strains. In previous years, the prevalence of B strains not included in the vaccine has been even higher. Vaccines failed to protect against more than half of the influenza B viruses seen in the 2011-2012 flu season.
Next year will be different. Trivalent vaccines will once again protect against a flu strain from the B/Yamagata lineage, specifically B/Massachusetts/2/2012-like. New quadrivalent vaccines from AstraZeneca's ($AZN) biotech unit MedImmune, GlaxoSmithKline ($GSK) and Sanofi ($SNY) will also protect against B/Brisbane/60/2008-like, a strain from the B/Victoria lineage. Doubling up on protection against influenza B strains is expected to increase the effectiveness of flu vaccines.
Infection with influenza B strains was found in one-fifth of flu-related hospitalizations last winter. These cases contributed to a particularly severe flu season. Almost 150 laboratory-confirmed, influenza-associated pediatric deaths were reported, compared to 26 the previous year. With the exception of the 2009 H1N1 pandemic--when 348 children died--there were more flu-related pediatric deaths than any year since it was made a nationally notifiable condition in 2004. Similarly, more people aged 65 and over were hospitalized with influenza-related conditions than any year since systematic data collection began in the 2005-2006 flu season.