What are the recommended vaccinations and assessments for a 4-month-old baby during a routine visit?

4-Month-Old Well-Child Visit

At the 4-month visit, administer the second doses of DTaP, IPV, Hib, pneumococcal conjugate vaccine (PCV), and rotavirus vaccine, along with the second dose of hepatitis B if not already given. 1

Core Vaccinations Due at 4 Months

The following vaccines should be administered at this visit:

• DTaP (Diphtheria, Tetanus, and Acellular Pertussis): Second dose of the series, with a minimum 4-week interval from the first dose given at 2 months 1

• IPV (Inactivated Poliovirus Vaccine): Second dose, with a minimum 4-week interval from the first dose 1

• Hib (Haemophilus influenzae type b): Second dose at 4 months; note that if using PRP-OMP formulation (PedvaxHIB or ComVax), only 2 doses are needed at 2 and 4 months, and the 6-month dose can be omitted 1

• PCV (Pneumococcal Conjugate Vaccine): Second dose of the series 1

• Rotavirus vaccine: Second dose, which must be administered before 32 weeks of age; do not start the series if the infant is older than 12 weeks 1

• Hepatitis B: Second dose if the 1-2 month dose was delayed; minimum 4-week interval from the first dose is required 1

Combination Vaccine Option

• DTaP-IPV/Hib combination vaccine (Pentacel) may be used to reduce the number of injections, combining DTaP, IPV, and Hib into a single injection 1

• This combination has comparable immunogenicity and safety to separately administered vaccines 1, 2

Key Clinical Considerations

Timing and intervals matter critically for vaccine efficacy:

• The minimum interval between the first and second doses of DTaP is 4 weeks, though an 8-week interval is preferred 1

• All vaccines can be administered simultaneously at separate anatomic sites without interference 3

• If the infant is behind schedule, catch-up vaccination should be initiated immediately following minimum interval guidelines 3

Important pitfalls to avoid:

• Do not administer rotavirus vaccine if the infant is older than 14 weeks and has not yet started the series 1

• For Hib vaccine, verify which formulation was used at 2 months; if PRP-OMP was given, the 6-month dose will not be needed 1

• The third dose of DTaP should not be administered before 14 weeks of age (approximately 3.5 months) 1

Developmental and Safety Assessments

Beyond vaccinations, the 4-month visit should include:

• Monitoring for adverse events from previous vaccinations; report any clinically significant events to VAERS 1

• Assessment of growth parameters and developmental milestones 4

• Anticipatory guidance regarding upcoming influenza vaccination eligibility at 6 months of age 1, 4