Vaccination against the flu is often a contentious point amongst members of the community, writes Dr Benson Riddle. Influenza is a seasonal viral illness, with most cases in Australia occurring between June and September. In the northern hemisphere most cases occur between December and April, however, in the tropics it can occur all year round (though it is less common in this region).
There are two types significant in humans - Influenza A and B - but what is unique about the influenza virus is its ability to continuously change. This is one of the reasons people can catch the flu year after year - our immune systems are unable to ever get used to a virus that continues to change.
Each year the Australian Influenza Vaccine Committee determines which three strains of influenza are to be targeted in the vaccine formulation for the upcoming season. This decision is based on the current important strains circulating in the northern hemisphere season that precedes ours.
The vaccine manufacturers then grow those virus strains in hens' eggs, before the virus is killed and processed into parts to go into the vaccine. Because the vaccine contains only part of a killed virusm, side-effects are now much less common, and because the virus has been killed, it is impossible to get influenza from the vaccine.
Generally the new influenza vaccine becomes available before the start of the season each year (usually by early March), and so, logically, it may as well be given as early as possible (especially because it generally takes one to two weeks before it can protect the person). It will then last about 12 months, when the new season's vaccine would then be necessary anyway. The vaccine is effective, but, as with all medications, this is not 100 per cent guaranteed. Generally, the older you are, the less effective it is.
So who should be vaccinated? Anyone over the age of six months (the vaccine is not recommended for those under this age) who wishes to reduce the likelihood of becoming ill with the flu should be vaccinated annually. However the vaccine is strongly recommended and should be actively promoted for all people aged 65 and over (free for this age group), Aboriginal and Torres Strait Islanders aged 15 and over (due to the increased risk of complications and death from influenza in this population), those with pre-existing medical conditions that put them at a higher risk (eg heart disease, lung disease, diabetes, kidney disease, neurological disease, weakened immune system), and people who regularly come into contact with at-risk groups (eg healthcare providers).
People often worry that getting vaccinated means that their own immune system is not being allowed to do its job, and, as a result, will weaken over time. However the opposite is actually the case, because vaccines are simply there to kick your own immune system into action with an inactive version of the disease that can't actually cause the disease - forcing your own immune system to work harder and become more effective in the long term.
