breast feeding until 6 months definitely helps boost baby's immunity. It is however suggested to breast feed the baby until 2 years and beyond with timely introduction of weaning foods to ensure baby's both short and long term health. In case if breast feeding is not possible beyond 6 months, ensure to include foods that boost immunity in your baby's daily diet.

You can try to breastfeed as much as possible... It's good ... Also you can start outside food gradually after the baby is 6 months..