Overall there has been a decline in Invasive Meningococcal Disease (IMD) cases since the 2003 introduction of the meningococcal C vaccine on the National Immunisation Program, with the overall rate of IMD decreasing 82% from 2002 to 2013. However, from 2014 the overall rate of IMD has increased. In 2016 year-to-date (YTD), there have been a total of 241 IMD cases compared to 149 IMD cases in 2013.