Preventive shots are clinically called vaccines. Whether postponing baby vaccines has an effect on the child depends on the time of postponement and the vaccine. Some vaccines are required within 24 hours of birth, such as BCG, but babies who are preterm, low-birth-weight babies or cannot be vaccinated on time due to illness can be vaccinated within 3 months without affecting the effectiveness of the vaccination. If more than 3 months in less than 3 years old, the tuberculin test should be conducted and the result is negative before vaccination. And some vaccines are 2 or 3 doses, the first and second doses have been vaccinated, and the third dose can not be vaccinated on time because of illness, or the first dose is not vaccinated on time, as long as the vaccination is completed within the latest time specified. For example, the prescribed time for the third dose of hepatitis B vaccine is 6 months of age after the baby’s birth, but it is also compatible to be vaccinated at 12 months of age, and exceeding the time limit will increase the risk of disease. In summary, delaying a vaccine by a few weeks generally has no effect on the child. If the time limit is exceeded, it will increase the risk of disease. Parents are advised to always immunize their children at the time specified in the immunization booklet if the child is in good health to ensure healthy growth.