Credit NIAID
# 9759
Twice each year influenza experts gather to discuss recent developments in human and animal influenza viruses around the world, and to decide on the composition of the next influenza season’s flu vaccine. Due to the time it takes to manufacture and distribute a vaccine, decisions on which strains to include must be made six months in advance.
Which means the composition of the northern hemisphere’s vaccine must be decided upon in February of each year, while decisions on the southern hemisphere’ vaccine are made in September.
NIAID has a terrific 3-minute video that shows how influenza viruses drift over time, and why the flu shot must be frequently updated, which you can view at this link.
Of course, there is always the danger that during the manufacturing or service period for this vaccine a new flu virus could emerge, and that is exactly what happened this past year with the H3N2 vaccine component.
While barely a blip on the radar when vaccine decisions were made 12 months ago, by October of 2014 a `drifted’ H3N2 virus was rapidly overtaking the competition (see CDC HAN Advisory On `Drifted’ H3N2 Seasonal Flu Virus), seriously driving down this year’s flu vaccine’s efficiency.
Yet despite the occasional miss , most years the flu vaccine turns out to provide at least a moderate level of protection (see CDC Vaccine Effectiveness - How Well Does the Flu Vaccine Work?), and along with good flu hygiene (washing hands, covering coughs, etc.), are your best protection against catching the flu.
This week the World Health Organization brought together representatives from GISRS (Global Influenza Surveillance and Response System), along with members of OFFLU (the OIE/FAO Network on Animal Influenza), and other experts to determine the Recommended composition of influenza virus vaccines for use in the 2015-2016 northern hemisphere influenza season.
Once again, the H1N1 component remains unchanged from the 2009 H1N1 virus, but the H3N2 has been shifted to match the `drifted’ version which plagued this year’s vaccine. The primary B component has also been updated.
26 February 2015
It is recommended that trivalent vaccines for use in the 2015-2016 influenza season (northern hemisphere winter) contain the following:
- an A/California/7/2009 (H1N1)pdm09-like virus;
- an A/Switzerland/9715293/2013 (H3N2)-like virus;
- a B/Phuket/3073/2013-like virus.
It is recommended that quadrivalent vaccines containing two influenza B viruses contain the above three viruses and a B/Brisbane/60/2008-like virus.
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