NBCSN Nationally Certified School Nurse Practice Exam

The first dose of the MMR (measles, mumps, and rubella) vaccine is recommended to be administered at 12 months of age. This timing is crucial because the vaccine is most effective when the child is at least a year old. At this age, the immune system has developed sufficiently to respond appropriately to the live attenuated virus in the vaccine, ensuring proper immunity against these diseases. Previous doses given prior to this time, such as at 6 months, do not provide the same level of protection and may be less effective due to maternal antibodies still present in the child's system. While vaccination at 11-12 years is important, it pertains to the booster doses typically administered at that age, rather than the initial dose. Administering the vaccine too early, such as before 12 months, or delaying it to ages later than recommended can impact the child's immunity and lead to a higher risk of outbreaks if they are not vaccinated in a timely manner.