Preterm babies are usually vaccinated according to their actual age, not according to the corrected age. However, when preterm babies are vaccinated, their physical condition should be stable, and their weight should be over 2 kg (the weight of BCG vaccine should be over 2.5 kg in general); if they do not reach this weight, they need to wait until their weight is in line with the weight and then be vaccinated. According to studies, the immune response, safety and tolerability of vaccination for most preterm babies are comparable to those of full-term babies. It is recommended that preterm babies should be vaccinated according to the immunization schedule of full-term babies. Therefore, if your preterm baby is physically eligible for vaccination, he/she can be vaccinated according to his/her actual age. The conditions for preterm babies to be vaccinated include two main points, i.e. vital signs are stable and weight is up to standard. Among them, the weight standard varies according to the type of vaccine injected. Generally speaking, except for BCG vaccine, premature babies need to weigh more than 2 kg in order to be vaccinated. Preterm babies who are vaccinated with BCG vaccine need to weigh more than 2.5 kilograms. When preterm babies are vaccinated, they should be vaccinated at a regular institution, undergo a proper pre-vaccination checkup, and be vaccinated only after meeting the indications for vaccination, and should not be vaccinated blindly in order to prevent adverse reactions.