October 2017 Update – The end of a nasty flu season

If you've escaped flu this year, there's some good news: the peak of our bad flu season seems to have passed in most, if not all, parts of Australia.

But because there have been significantly more influenza cases than usual, there's still a lot of illness around.

If you look at the result of lab tests, there's been more than 2.5 times the number of confirmed cases of influenza compared to last year,

But this figure is misleading because some of the rise is due to an increase in the availability of rapid testing for flu.The number of hospital and GP visits for influenza is a much better guide and these suggest about a 50 per cent rise in flu cases

Estimates in total, about 5 per cent of Australians will have had flu this year.

Why has it been a bad flu season?

A key factor seems to be that the flu vaccine has been less effective than expected this year. Preliminary data suggests it offered only 15 to 20 per cent protection,

Is it worth bothering with a flu shot each year?

Flu is a serious illness which can sometimes kill even apparently healthy people.

Even though we've got a vaccine that's not predictable in how well it works each year and on average might have only a 40 per cent efficacy, we'd still recommend it because that reduction is better than nothing.

That's particularly important if you're in an 'at risk' group for whom flu can cause very serious effects. If you've got really bad heart disease or diabetes, the last thing you need is another serious infection.

Has this year's flu affected younger people versus older people differently?

There's no evidence the proportion of younger people affected is greater this year. But absolute numbers are likely higher because of the higher number of infections overall.

It is the elderly who seem hardest hit. And it seems the vaccine was particularly ineffective in this age group.

We essentially had the same vaccine as England and Europe had last year. That vaccine appears to have been virtually completely ineffective in over 65s there. It just didn't work at all. We don't know why this is the case.

It looks like the vaccine efficacy [in this age group] is going to be no better for us than it was in England and Europe. In general, older people produce a less effective immune response to vaccines than younger people.

But this year, the strain of flu that dominated in Australia (H3, a type of influenza A) is one known to cause more significant illness in the elderly. As well, it's known this strain underwent some changes this season.

These factors may have contributed to the large number of cases in older people who had been vaccinated.