Professor Peter Collignon

So unless you've really got a major underlying illness and come into hospital, even the value of those drugs is pretty marginal.

And for the common cold virus, unfortunately, all you've got is your mother's sympathy and maybe some chicken soup.

Well, for some people, influenza is particularly bad.

If you've got underlying heart disease, lung disease, diabetes, for instance, or a lot of neurological diseases in children, if they get influenza, they are more likely to get very sick and have to come into hospital.

So that's the focus.

The trouble with the influenza vaccine, it's probably only 50% effective.

So compared to the great vaccines we've got that you have one or two doses and you often have lifelong immunity, tetanus, diphtheria, measles, polio, for instance, influenza is not one of those.

The virus changes frequently.

And so you need an injection every year.

And the other problem is that most people would only get an actual influenza infection once every 10 or 20 years.

There's some debate about that, but probably at the most every 10 years.

So basically, if it's only 50% effective, then you've got to have it for 20 years before you get benefit in one year.

And most people have a mild infection or asymptomatic.

So it's not the same as a lot of the other vaccines we've got.

But having said that,

If you've got underlying heart disease, lung disease, and you're much more increased risk of getting a problem, and that's often people over the age of 70, for instance, have those, then it is recommended because even if it's only a 50% chance it'll decrease your chance of getting into hospital, that's worth having if you're sitting on the edge and you can be tipped over more easily.

Short answer is I don't think you do need it every year.

There's some argument that, for instance, if you're a healthy child, your chance of getting into hospital if you don't have underlying disease like diabetes or asthma, for instance, is pretty low.

And if you have a natural infection, you may get broader immunity

than if you just have a vaccine every year.