Hello girls! Please advise how to boost your child's immunity? What vi…

Hello girls! Please advise how to boost your child's immunity? What vitamins besides D3 should be given? Since birth, several times he had anesthesia, antibiotics almost every two months. Now we are 9 months old. Is Dr. Mamamarin really good for boosting it? Who tried it? How much to drink? For myself I took from iHerb omega 3, it really helped. For the child, I am afraid to take vitamins from there, who tried and what for a child? Has anyone tried Nutricia Infatrini, taken from the children's world, but not given yet because I haven't discussed it with the doctor, but they say that pediatricians recommend them according to the cashier. P.