What vaccinations should be administered to a 9-month-old infant with no prior vaccination history?

Vaccination Recommendations for a 9-Month-Old Unvaccinated Infant

For a 9-month-old infant with no prior vaccination history, you should administer DTaP-1, Hepatitis B, Hib, and PCV at this visit, but NOT measles vaccine (which requires waiting until 12 months) and NOT OPV (which has been replaced by IPV in the United States). 1

Critical Age-Based Considerations

Measles vaccine cannot be given at 9 months of age. The minimum age for MMR administration is 12 months, and this is a firm contraindication at 9 months. 2, 1 This immediately eliminates any answer choice containing measles vaccine.

OPV is no longer recommended in the United States. The U.S. switched to an IPV-only or sequential IPV/OPV schedule in 1997, with current guidelines recommending IPV exclusively. 3 Any answer choice containing OPV reflects outdated practice for the U.S. context.

Vaccines to Administer at This 9-Month Visit

DTaP (First Dose)

• Begin the DTaP series immediately with the first dose, as the minimum age is 6 weeks. 1
• For unvaccinated children ages 7-11 months, administer the first dose now, followed by additional doses at 2-month intervals. 2
• The child will ultimately need a 3-dose primary series plus boosters at 15-18 months and 4-6 years. 1, 4

Hepatitis B (First Dose)

• Initiate the 3-dose HepB series regardless of current age. 2
• The schedule is 0,1-2 months, and 6-18 months after the first dose. 1
• Hepatitis B vaccination should be given to all previously unvaccinated children. 2

Haemophilus influenzae type b (Hib)

• For children 7-11 months, administer two doses 2 months apart, followed by a booster at 12-18 months. 2
• This represents catch-up vaccination for delayed immunization. 1

Pneumococcal Conjugate Vaccine (PCV)

• Begin the PCV series with age-appropriate catch-up dosing. 1
• PCV is part of the routine infant schedule and should be initiated. 4

Inactivated Poliovirus Vaccine (IPV)

• Start the IPV series (not OPV) with the first dose. 1
• The minimum age is 6 weeks, and a 4-dose series is recommended. 1

Vaccines to Defer

BCG Vaccine

• BCG is not part of routine U.S. immunization schedules and is only recommended in specific high-risk situations (e.g., endemic areas, household exposure to multidrug-resistant TB).
• The question context suggests a U.S. setting where BCG is not routinely indicated.

Measles-Containing Vaccines

• Must wait until 12 months of age for the first MMR dose. 2, 1
• This is a strict age requirement that cannot be bypassed.

Practical Implementation

Administer all appropriate vaccines simultaneously at separate anatomic sites to accelerate catch-up immunization. 1 This approach is safe, effective, and prevents further delays. 2

Document all vaccinations carefully and provide the parent with a catch-up schedule showing when the next doses are due. 1 The next visit should occur in approximately 4 weeks (minimum interval) to 2 months (optimal interval) for subsequent doses. 1, 5

Answer Selection Based on Evidence

None of the provided answer choices perfectly matches current U.S. guidelines, but the best approximation would exclude:

• Any option with measles vaccine (contraindicated at 9 months)
• Any option with OPV (outdated for U.S. practice)
• Any option with only BCG and Hepatitis B (insufficient coverage)

The correct approach is: DTaP-1, IPV-1, Hib-1, PCV-1, and Hepatitis B-1 at this visit, with measles deferred until 12 months. 1, 4