Researchers are working on a flu vaccine that will be effective for multiple years (even forever), but the fact that the flu virus can mutate so rapidly makes this difficult. The current vaccines target the part of the virus that changes year to year. For a universal (i.e. applicable to all flu strains) flu vaccine to work, scientists first have to figure out what is the same across all flu viruses and this is where they aren’t sure yet. Flu viruses are a lot more complex than they seem. Different research teams are working on different solutions to this problem, but experts expect that we are at least 5-10 years away from a universal vaccine.
So each year, the World Health Organization (WHO) makes recommendations for the Northern and Southern Hemisphere flu vaccines based on their best guess of which flu strains will circulate so that companies can grow enough of those strains to use in the vaccine (for more on how the flu vaccine works see You Can't Get the Flu from the Flu Vaccine). It can take upwards of six months to grow enough vaccine for the flu season, so the WHO has to pick before they know what is circulating. However, they can make educated guesses based on surveillance-based data.
What is in this year’s vaccine?
In 2014, the WHO selected:
- an A/California/7/2009 (H1N1)pdm09-like virus;
- an A/Texas/50/2012 (H3N2)-like virus;
- a B/Massachusetts/2/2012-like virus.
- a B/Brisbane/60/2008-like virus.
It is also important to keep in mind that the strains that circulate can change throughout the flu season and the flu vaccine may be well matched to those strains. If the flu you happen to come into contact with is H1N1, it won’t matter if the H3N2 strain is not well matched. And the fact is, the flu vaccine, well matched or not, still provides your best chance of avoiding the flu.
*2015-2016 UPDATE: Please click here to read about the flu viruses covered in the 2015-2016 flu vaccines.
Click here to read more about Flu Myths in our 18 Years, 18 Reasons series.