The influenza vaccines available in Australia are all made from influenza viruses that have been grown, highly purified, chemically killed and then ‘split' or disaggregated with a detergent or solvent. The end-product is a ‘vaccine' consisting of pieces of purified inactivated influenza viruses.
When these are injected the body is fooled into believing it has been invaded and produces an immune response including antibodies against the important surface proteins, the haemagglutinin (H) and the neuraminidase (N). It is these antibodies that provide most of our protection against influenza.
This method of manufacture gives us a vaccine which, despite occasional misconceptions to the contrary, cannot cause influenza in the recipient [link to myths and misconceptions]. In addition, the splitting process essentially ‘detoxifies' the vaccine, removing the mild constitutional reactions (fever, headache, malaise) that were occasionally produced by the earlier whole virus vaccines. These days the most common vaccine reaction is a slightly sore arm for a day or so.
Because the H and N proteins of influenza viruses continually change by mutation it is necessary to update our vaccines every year. This is achieved through a World Health Organization international surveillance program: the WHO Global Influenza Program which provides analysis of influenza viruses recovered worldwide. The information from these analyses are reviewed twice yearly, in February and then in September at WHO consultations and recommendations are then made regarding updating the vaccines.
Based on these recommendations, national or regional authorities then determine the actual three virus strains (the most appropriate one from each of the three families of influenza that are circulating in the population) to include in vaccines that will be used 5-6 months later. This delay is due to the long lead-time currently involved in the manufacture of the vaccines and it means that accurately tracking the evolution of the viruses is particularly important.
The formulation of vaccines for use in Australia is determined each year by the Australian Influenza Vaccine Committee based on information and recommendations from the WHO September consultation.
Last updated: January 2014