My child has been falling sick very frequently. How do i resolve this？

Is your child in infant care? If so, it is very common for them to fall sick when in infant/child care! If not, you may consider "upgrading" hygiene and sanitizing habits - I'm not exactly sure if there are any supplements you can give at 9 months old, but one way would be to keep better hygiene and take note of the onset of illness to find out what's causing your child to get sick - sometimes it's an allergy to dust mites, laundry detergent, household things that cause them! Other than that, it's cliché but usually just keeping hydrated and resting enough to help fight it off :)