What is the appropriate management for a 3‑year‑old child who has not received any DTaP (diphtheria‑tetanus‑acellular pertussis), MMR (measles‑mumps‑rubella), or oral polio vaccine due to frequent travel?

Catch-Up Vaccination is Mandatory for This Unvaccinated 3-Year-Old

The correct answer is B: try to catch up missed vaccines. This child requires immediate initiation of a catch-up vaccination schedule to protect against life-threatening vaccine-preventable diseases, regardless of travel history. 1

Why Catch-Up Vaccination is Essential

Morbidity and Mortality Risk

• An unvaccinated 3-year-old remains vulnerable to diphtheria, tetanus, pertussis, polio, measles, mumps, and rubella—all diseases with significant morbidity and potential mortality 1
• Approximately 15-36% of children aged 9-13 years lack protective tetanus antibodies despite vaccination; this child has zero protection 2
• Measles, in particular, carries substantial mortality risk in unvaccinated children, and mumps/rubella cause serious complications 3

Why Other Options Are Wrong

Option A (reassuring/unnecessary) is dangerous and medically indefensible:

• Withholding vaccines exposes the child to preventable diseases with serious consequences 1
• Travel history is irrelevant to the need for routine childhood immunizations 1

Option C (waiting until school) is unacceptable:

• Delaying vaccination leaves the child unprotected for 2-3 additional years during peak vulnerability 1
• Disease exposure can occur anywhere, not just in school settings 1

Option D (selective vaccination) violates standard guidelines:

• All routine childhood vaccines should be administered according to catch-up schedules 1
• There is no medical justification for prioritizing polio over other vaccines 1

Recommended Catch-Up Schedule for This 3-Year-Old

DTaP Series

• Begin immediately with DTaP dose 1 1
• Administer DTaP dose 2 at minimum 4-week interval 1
• Administer DTaP dose 3 at minimum 4-week interval after dose 2 (but not before age 14 weeks, which is already met) 1
• Administer DTaP dose 4 at minimum 6-month interval after dose 3 1
• The fifth dose at age 4-6 years can be given when the child reaches that age 1

IPV Series (Not OPV)

• Critical point: OPV is no longer used in the United States since January 2000 1
• Administer IPV (inactivated poliovirus vaccine) on the same schedule as DTaP 1
• Four doses total: can be given at 4-week minimum intervals for catch-up 1
• The final (fourth) dose should be administered at age ≥4 years with minimum 6-month interval from dose 3 1

MMR Series

• Administer MMR dose 1 immediately (can be given simultaneously with DTaP/IPV at different injection sites) 1, 3
• Administer MMR dose 2 at minimum 4-week interval after dose 1 1
• Both doses can be completed during the catch-up period 3

Practical Implementation Using Combination Vaccines

• DTaP-IPV/Hib (Pentacel) can be used for catch-up vaccination in children through age 4 years 1, 4
• This reduces the number of injections from 6 to 3 for the first three doses 4
• Minimum 4-week intervals between doses are acceptable for catch-up, though 8 weeks is preferred 1

Common Pitfalls to Avoid

Do Not Use OPV

• The question mentions OPV, but this vaccine has been discontinued in the United States since 2000 due to risk of vaccine-associated paralytic poliomyelitis 1
• Always use IPV for polio vaccination 1

Do Not Delay Based on Travel History

• Frequent travel is not a contraindication to vaccination 1
• In fact, travelers may have increased exposure risk to vaccine-preventable diseases 1

Do Not Administer Vaccines Selectively

• All routine childhood vaccines should be given according to catch-up schedules 1
• There is no evidence supporting selective vaccination strategies in healthy children 1

Simultaneous Administration is Safe and Recommended

• Multiple vaccines can be administered during the same visit at different anatomic sites 1
• This improves compliance and accelerates protection 3, 4

Timeline for Completion

Accelerated catch-up schedule (minimum intervals):

• Visit 1 (today): DTaP-IPV/Hib dose 1 + MMR dose 1
• Visit 2 (4 weeks later): DTaP-IPV/Hib dose 2 + MMR dose 2
• Visit 3 (4 weeks after visit 2): DTaP-IPV/Hib dose 3
• Visit 4 (6 months after visit 3): DTaP-IPV/Hib dose 4
• Visit 5 (at age 4-6 years): DTaP and IPV boosters 1

This aggressive catch-up approach prioritizes rapid protection while maintaining minimum safe intervals between doses.