Influenza Update

09/Apr/2018     Health

2017 was the worst year for influenza in recorded history in terms of numbers of cases diagnosed. In Australia there was greater than double the previous highest number of laboratory cases with just short of 250 000 cases as compared to the previous highest number which was just over 100 000.

There was a much higher number of recorded hospitalisations and about 6 times the usual number of deaths attributed to influenza. The northern hemisphere has then had a similarly bad 17/18 season with a very high number of cases, mostly of the same strains we saw last year in Australia. This means there will be an element of protection in people in Australia that were exposed last year (although this isn’t sufficient to be relied upon).

This year there are more options for vaccination too that should make a big difference including higher dose or boosted vaccines for the elderly population and most states are subsidising the vaccine for children which should make a difference.

Finally for reasons that aren’t entirely clear, the vaccine last year didn’t work as well as we would have liked. This doesn’t mean it didn’t offer some level of protection in terms of reducing severity or duration of illness, it simply didn’t protect people quite as well as previously. This is likely to not be the case this year with some changes made to the routine vaccine including the addition of the strain that caused the greatest number of cases last year.

Therefore overall it is likely we will see fewer cases in Australia than last year although with the improved vaccine options it will be critical that we see sufficient numbers of people get vaccinated so we can realise the potential benefit of these improvements

Given the main strains causing the majority of cases in the northern hemisphere are those that circulated in Australia last year, it is likely that a proportion of the population here have been exposed last year and therefore have some protection from those strains this year. This is not sufficient to be relied upon however and the probability of having a milder season in Australia can be greatly enhanced by having a higher uptake of the vaccine this year, particularly given the improved options available particularly for people over 65.

Dr Paul Griffin
Director Infectious Diseases
Mater Group

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