Our son has had several bouts of pneumonia due to his chronic lung disease - former 26 weeker. We were told the lungs continue to rebuild new lung tissue until 8 years of age. After that, the lungs will pretty much have repaired as much as they are going to. Unfortunately, I think this is one of the side effects of prematurity. We try to prevent colds at all costs, as these can easily turn to pneumonia. My advice is....hand wash, hand wash, hand sanitizer and keep away from other people that are sick.