This article states the following but doesn't help me understand why you would bother with the tri over the quad, and is the extra strain covered in quadrivalent the 'bad' flu from Northern Hemisphere's past winter that I think I half-heard on tele a few weeks ago?
>>> 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).<<<<<<<<https://www.tga.gov.au/media-release/20 ... a-vaccines