HIB Vaccine Administration at 18 Months vs 15 Months
Yes, the HIB booster can be given at 18 months instead of 15 months, as ACIP guidelines specify the booster should be administered at 12-15 months of age or "as soon as possible thereafter" with a minimum 8-week interval from the previous dose. 1
Recommended Timing Window
The standard booster dose timing is 12-15 months of age, which represents the optimal window for administration. 1, 2
However, the guidelines explicitly state the booster should be given "as soon as possible thereafter" if not administered during the 12-15 month window, making 18 months acceptable. 1
The critical requirement is maintaining at least 8 weeks (2 months) between the final primary series dose and the booster, regardless of when the booster is ultimately given. 1, 2
Clinical Considerations
Delaying from 15 to 18 months is permissible but not optimal, as earlier administration provides protection sooner during a period when children remain at risk for invasive Hib disease. 1
Any licensed Hib conjugate vaccine (monovalent or combination) can be used for the booster dose at 18 months, regardless of which vaccine was used for the primary series. 1, 2
For Hiberix specifically, it can be administered as early as 12 months to facilitate timely booster vaccination, though it should only be used as a booster (not primary series) in children who received at least one prior Hib dose. 1, 3
Common Pitfall to Avoid
Do not confuse "as soon as possible thereafter" with indefinite delay—while 18 months is acceptable, the intent is to minimize the gap beyond 15 months, not to routinely schedule boosters at later ages. 1
The minimum 8-week interval must be respected; administering the booster too early (less than 8 weeks after the last primary dose) may result in suboptimal immune response. 1