6-Month Well-Child Checkup: Vaccinations and Developmental Assessment
Recommended Vaccinations at 6 Months
At the 6-month visit, infants should receive the third doses of DTaP, Hib (if using certain vaccine formulations), PCV, IPV (or can be delayed to 6-18 months), and the third dose of hepatitis B vaccine (which can be given anytime between 6-18 months), along with the first influenza vaccine if during flu season. 1
Core Vaccine Series - Third Doses
DTaP (Diphtheria, Tetanus, acellular Pertussis): The third dose should be administered at 6 months of age, completing the primary infant series before the fourth dose at 15-18 months 2, 1
Hepatitis B: The third dose should be administered at 6-18 months of age, with the guideline noting that the last dose in the series should not be administered before 6 months of age 2, 1
Haemophilus influenzae type b (Hib): The third dose at 6 months depends on which vaccine formulation was used 2, 1
Pneumococcal Conjugate Vaccine (PCV): The third dose should be administered at 6 months 1
Inactivated Poliovirus Vaccine (IPV): While the schedule allows for IPV at 6-18 months for the third dose, it can be given at the 6-month visit 2, 1
Seasonal and Additional Vaccines
Influenza vaccine: Should be initiated at 6 months of age if during flu season 1
Rotavirus: If not yet completed, the final dose must be administered by 8 months of age, making the 6-month visit potentially the last opportunity 1
Key Vaccination Considerations at 6 Months
Timing and Intervals
- The third dose of hepatitis B must be given at least 8 weeks after the second dose and at least 16 weeks after the first dose 2
- Multiple vaccines can and should be administered simultaneously at separate anatomic sites 4
- Combination vaccines (such as hexavalent DTaP-HBV-IPV/Hib) demonstrate comparable safety and immunogenicity to separate injections, potentially reducing the number of injections 5, 6
Special Populations
- Preterm infants: Should receive full-dose vaccines at chronologic age (not corrected age), as half-dose regimens result in inadequate immune response, particularly to pertussis 7
- Infants of HBsAg-positive mothers: Must complete the hepatitis B series by 6 months and should be tested for HBsAg and anti-HBs at 9-15 months 1, 3
Developmental Milestones at 6 Months
While the provided evidence focuses primarily on vaccination schedules, the 6-month visit should include comprehensive developmental screening. The immunization schedule is designed around the critical developmental window when maternal antibody protection wanes and infants become increasingly vulnerable to serious infections 1.
Immunological Context
- The 6-month timepoint represents completion of the primary vaccine series for most antigens, achieving seroconversion rates of 96-100% when the schedule is followed correctly 1
- This timing balances maternal antibody interference with the urgent need to establish infant immunity during maximum vulnerability to life-threatening infections 1
Common Pitfalls to Avoid
- Do not delay the hepatitis B third dose beyond 18 months, even though the window is 6-18 months; earlier completion ensures protection 2, 1
- Do not assume all Hib vaccines require a 6-month dose; verify which formulation was used at 2 and 4 months 2
- Do not use reduced-dose vaccines in preterm infants; this results in inadequate immune response, particularly to pertussis, requiring additional doses 7
- Do not miss the rotavirus deadline; if not completed by 6 months, it must be finished by 8 months of age 1
- Do not forget influenza vaccine if the visit occurs during flu season (typically fall/winter), as this is the earliest age for influenza vaccination 1