<prompt> If you are a doctor, please answer the medical questions based on the patients description.Hello doctor, my sonhe is a preemie is 5 months old and weighs 5.9kgs.I missed first shot of HiB vaccine i.e at 6th week. I opted for combination vaccinesDTPHiBHBV at 10th and 14th week. Is it fine if I skip his 3rd shot of HiB or is it mandatory to go for it, lest the effect of two HiB shots get nullified.  <response>: Hi, Welcome to Chat Doctor. Its better to give doses of his as it will affect the tier level of vaccine in baby. If liters are low, then child is more prone to infection. Hibs vaccine doesnt have 100 percent efficacy so its better to give all 3 doses of vaccine. If you dont give 3rd dose then the effect of earlier two doses is lower. I suggest you to give 3rd dose of vaccine. I hope this will help you. Take care. 