Hello dear, After going through your history, I believe you have some genuine concern and I will try to help you out of this situation. Getting repeated infection at this age is common as babies are exposed to other children in schools or play ground. you can start a multi vitamin syrup containing ZINC as it would help him recover earlier from each episode and also decrease the risk of reinfection. You should concern about Bronchitis which may recur. In the mean time the steam inhalation can be continued. To boost the immunity traditional ways of medicines like Ayurved or Homeopathy should be adopted, which is beyond my scope. I hope I could solve your query. Please do not hesitate to clarify more doubts for the same situation. Thank you for the way you are in my life. Dr Ipsit Panda