Hi!
Immunity depends on several factors like eating habits , smoking, alcohol consumption , also habits, stress and underlying medical issues.
Take 3 litres of water daily, eat fresh fruits and raw vegetables with meals as they have plenty of vitamins and minerals for immunity, include green tea, turmeric, ginger in the diet.
This will help maintain general health as well.
Next Steps
Consult on practo.com for further advice
Health Tips
Avoid taking any medication or supplement without expert advice or prescription