Influenza vaccines can change from year to year as new strains of influenza virus appear. This is one reason vaccination against influenza is given every year.

Following a review of the strains of influenza that were circulating in the Southern Hemisphere, the Australian Influenza Vaccine Committee (AIVC) recommended that the TGA should adopt the September World Health Organization (WHO) recommendations for the strains to be Covered by the 2015 seasonal influenza vaccines. Details of the strains were announced on the TGA website on 14 October 2014.

2015 is the first year that two categories of influenza vaccines will be available. These are:

• vaccines that protect against three strains of the virus (known as trivalent influenza vaccines)
• vaccines that protect against four strains of the virus (known as quadrivalent influenza vaccines)

Trivalent vaccines include two influenza A strains and one B strain. For 2015, one of the A strains is the H1N1 strain that has been in the seasonal vaccine since 2010. The other two strains have changed compared with the 2014 vaccines used in Australia and the 2014/15 vaccines used in the recent Northern Hemisphere winter. The quadrivalent vaccines contain the same strains as the trivalent vaccines with the addition of a second influenza B strain.

For more details, go to: https://www.tga.gov.au/media-release/2015-seasonal-influenza-vaccines