Professor Luke O'Neill

And that gives the older child an advantage because there's a great line about teaching.

In fact, there was Richard Feynman, the physicist, who said, if you want to master something, teach it.

So the older child is learning to master things by teaching the younger child.

That gives them an advantage as well.

So again, these are other reasons why this would be.

And you can see now we're all fascinated by this, aren't we?

And then another one, the older one is in plenty more ambitious, maybe because the parents are pushing them.

And they're 7% more likely to go to university than the second child.

And that just shows you maybe there's a bit of a push on from the parents there.

So that's another factor, the parents being a bit more ambitious for the first child than the second one.

And then, of course, what this all means is vaccinate the child.

Because if you vaccinate the children, they're less likely to pick up these infections to give them a disadvantage.

So yet again, it's yet another reason to vaccinate, not just to stop the child getting sick.

It can help them in their lives later on.

It's a remarkable part of that.

Now, the thing to say is some infections are good, remember.

Don't be keeping children too clean.

Because if you keep them too clean, their immune systems aren't being educated.

A bit of dirt is good.

It's more the severe end that we worry about, hence the need for vaccines for these things like RSV.