I understand I have no authority on the subject, but, aren't we well aware that immunity wears off at different rates depending on the strain ? A lot of sickness only affect the children, and once for their lifetime, but there is at least covid for we know the immunity wears off. Surely there are many others.

edit: I suspect the article only states that life long immunity does not wears off. I don't challenge that at all.

This isn't really as simple as a linear decrease in immunity though - certain tools that your immune system uses like antibodies decrease over time but other tools like T-cell responses are long lasting. Thinking of it in terms of an acute response where you're very strongly protected and a persistent response where you have a slower but still effective protection is a better model.

But don't parents getting sick at work and bringing it home to their kids help the kids get exposed?

Or do you think kids get enough exposure at school? (assuming schools don't keep going remote too)

Based on how consistently my niece has been sick since starting school this year, I'd say they get enough exposure at school.

That's one of those sciencey articles that is only technically correct within a specific context, otherwise why are elderly people advised to get the flu vaccine every year?