Prebiotics and HMo based diet is good for immunity boosting.

Include seasonal food in moderation and continue breastfeeding the little one as it contains FOS and Fibre which helps to built the immunity and keeps gut healthy

Give him seasonal fruits, veggies, milk, curd, dry fruits prebiotics rich food etc

Baby immunity building takes some time. You can give all types veggies, furits, and most important Prebiotics rich food like curd, oats, apple, banana etc. It's very helpful for increase baby immunity.

Breast milk has all the necessary nutrients which boost immunity