Why can a 12-month-old with a history of febrile seizure not receive the MMR vaccine immediately after the varicella vaccine?

The correct response highlights the importance of timing in administering live vaccines, particularly for pediatric patients. In this case, when a child has received one live vaccine, such as the varicella vaccine, it's essential to wait at least 4 weeks before administering another live vaccine like the MMR (measles, mumps, rubella) vaccine. This waiting period is necessary to ensure that the body can develop an adequate immune response to each vaccine without interference, as both contain live attenuated viruses.

The guidelines for immunization schedules emphasize this waiting time to maximize vaccine efficacy. Even if a child has a history of febrile seizures, the concern is primarily about providing optimal vaccination strategy rather than a direct contraindication to receiving the MMR.

The other options, while they may suggest different scenarios for vaccine administration, do not correctly address the specific situation concerning the administration of live vaccines in succession. For example, an anaphylactic egg allergy usually pertains to vaccines that contain egg proteins, and living with an immunosuppressed family member does not specifically relate to the timing of live vaccines. Thus, the requirement to wait between live vaccinations is the key factor in this scenario.