We use pentavite. It's a liquid - citrus flavor and our boys love it. It also has added iron. Another thing to look at maybe a probiotic. We use inner health for kids as they say immunity starts in the gut. My DS1 hardly ever gets sick these days & if he does it's a mild version runny nose etc. he is 4.5. DS2 is just building his up & we probably get a week of him being well before he gets it again. He is 2 in July.