Similar to another poster who has a 6mo my nearly 4yo who I've posted about before is getting reoccurring chest infections this persistent cough has been going on for years but this autumn has been shocking she's had 3 chest infections since the beginning of September.
The only thing that gets rid of this hacking cough that she has for weeks and keeps her awake all night is antibiotics 
Doctors recent advice (lost count how many times we've seen them or out of hours at our local hospital) is her immune system is so low that we need to pull her out of pre school and not be in contact with children for 2 weeks to see if we can break the cycle and build her Immune system back up. This does make sense but if this doesn't work I'm going to insist on an X-ray and bloods being taken.
Anyway my main question is what multivitamins do you give your 4yo? She flat refuses the liquid stuff even on yoghurt and I really want to blitz this in the next too weeks with some heavy duty vitamins. Sorry for the long post but any advice hugely appreciated we really are at our wits end.