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Difficulty: MediumPreventive Care and Immunizations

A 9-month-old boy is brought to the clinic by his parents for a pre-travel consultation. The family will be traveling next week to a country experiencing an ongoing measles outbreak and plans to stay for two months. The patient was born at term, has no significant medical history, and is developing normally. He has received all routine childhood immunizations recommended for his age in the United States. His vital signs are within normal limits, and physical examination is unremarkable. Which of the following is the most appropriate recommendation regarding measles immunization for this patient?

  1. Administer one dose of the measles, mumps, and rubella (MMR) vaccine today, and administer the next routine dose at age 12 to 15 months.Answer
  2. B
    Administer one dose of the MMR vaccine today, which will count as the first dose of his routine two-dose series.
  3. C
    Defer the MMR vaccine because live-attenuated vaccines are strictly contraindicated in infants under 12 months of age.
  4. D
    Administer intramuscular measles immune globulin today and defer the MMR vaccine until his 12-month well-child visit.
  5. E
    Advise the parents that no intervention is necessary because maternal antibodies provide sufficient protection against measles until 12 months of age.

Answer

The most appropriate action is to administer one dose of the MMR vaccine today, followed by the routine dose at 12 to 15 months.
The correct action is to administer the MMR vaccine today and continue with the routine series at 12 to 15 months. The standard childhood immunization schedule recommends the first dose of the live-attenuated measles, mumps, and rubella (MMR) vaccine at 12 to 15 months of age. Administration is delayed until this age because circulating transplacental maternal antibodies can interfere with the infant's ability to mount a robust and lasting immune response to the vaccine virus. However, infants between 6 and 11 months of age have waning maternal antibodies and are highly susceptible to measles infection. Therefore, for infants in this age group who are traveling internationally to areas with endemic measles or active outbreaks, the CDC recommends administering an early dose of the MMR vaccine to provide temporary protection. Because of the potential for blunted immunogenicity from residual maternal antibodies, this early dose is considered invalid for the routine series. The child must still receive the standard two doses (at 12-15 months and 4-6 years) to ensure lifelong immunity.

Step-by-Step Solution

1
Identify the patient's age and travel risk.
The patient is a 9-month-old infant traveling to a measles-endemic area.
Risk assessment determines whether standard immunization schedules need to be adjusted.
2
Determine the indication for measles vaccination in this age group.
Infants 6-11 months of age traveling internationally should receive an early dose of the MMR vaccine.
Maternal antibodies wane by this age, leaving the infant vulnerable in high-prevalence areas.
3
Evaluate how this early dose affects the routine schedule.
The early dose does not count toward the routine 2-dose series.
Maternal antibodies can blunt the immune response to the vaccine before 12 months of age, so the routine series must still be completed starting at 12-15 months.

Key Concept

Infants aged 6 to 11 months who are traveling internationally should receive one dose of the MMR vaccine prior to departure. This dose does not count toward the routine 2-dose series, which must still be administered starting at 12 to 15 months of age.
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Topics

Preventive Care and Immunizations

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