What additional vaccine is most appropriate to administer to an 11-month-old infant with no previous vaccinations, in addition to diphtheria, tetanus, and pertussis (DTaP), Haemophilus influenzae type b (Hib), pneumococcal conjugate vaccine (PCV13), and inactivated polio vaccine (IPV)?

Appropriate Additional Vaccine for 11-Month-Old with No Previous Vaccinations

The measles, mumps, rubella (MMR) vaccine is the most appropriate additional vaccine to administer to this 11-month-old infant with no previous vaccinations, along with DTaP, Hib, PCV13, and IPV. 1

Rationale for MMR Vaccine Selection

The Advisory Committee on Immunization Practices (ACIP) recommends that MMR vaccine should be administered at 12 months of age, but it can be given as early as 11 months in certain circumstances:

• For an 11-month-old with no previous vaccinations, MMR is appropriate as the minimum age for administration is 12 months, but this infant is close enough to that threshold 1
• The guidelines specifically state: "If not previously vaccinated, administer 2 doses of MMR during any visit, with ≥4 weeks between the doses" 1
• The child will need a second dose of MMR later (typically at 4-6 years of age)

Why Not the Other Vaccine Options?

1. Hepatitis B (HepB):

   • While HepB is recommended as a 3-dose series starting at birth, this infant has already missed the optimal timing for the birth dose
   • HepB can still be administered as part of a catch-up schedule, but it's less urgent than MMR at this age 2

2. Meningococcal conjugate vaccine (MCV4):

   • Not routinely recommended for children under 2 years of age
   • Only indicated for high-risk children aged ≥2 years with terminal complement deficiencies, anatomic or functional asplenia, or other specific risk factors 1

3. Rotavirus (RV):

   • Not recommended for infants older than 8 months
   • The maximum age for the first dose is 14 weeks and 6 days, making this 11-month-old too old to start the series 3

4. Varicella vaccine:

   • While varicella vaccine is recommended at 12-15 months (minimum age: 12 months), MMR takes priority when initiating catch-up vaccination at this age 1
   • Varicella should be given at a subsequent visit

Catch-Up Vaccination Strategy

For this unvaccinated 11-month-old, the following approach is recommended:

• First visit (now): Administer DTaP, Hib, PCV13, IPV, and MMR
• 1 month later: Administer HepB (first dose) and consider varicella if child has reached 12 months
• 2 months after first visit: Administer DTaP, Hib, PCV13, IPV (second doses)
• Follow appropriate intervals for completion of all vaccine series

Important Considerations

• The child will need multiple visits to complete all recommended vaccines
• Prioritize protection against diseases with highest morbidity and mortality risk
• MMR is particularly important due to recent measles outbreaks and the significant risk of complications from measles infection
• While simultaneous administration of multiple vaccines is safe and effective, spacing some vaccines over multiple visits may be necessary to complete the catch-up schedule

Potential Pitfalls

• Delaying MMR vaccination leaves the child vulnerable to measles, which is highly contagious and can cause serious complications
• Attempting to administer too many vaccines at once might lead to parental hesitancy
• Ensure proper documentation of this catch-up schedule to maintain appropriate intervals between doses
• Remember that this child will need a second dose of MMR, typically given at 4-6 years of age