Next Step After 3rd Dose at 15 Months
For an infant who started Nimenrix before 6 months of age and received a 3rd dose at 15 months, a 4th dose should be administered at 12 months of age or as soon as possible thereafter if the 3rd dose was given late. 1
Standard Nimenrix Dosing Schedule for Infants Starting Before 6 Months
The recommended schedule for infants beginning Nimenrix vaccination before 6 months of age is a 4-dose series at 2,4,6, and 12 months of age. 1, 2 This applies to both high-risk infants and those in routine vaccination programs where early protection is needed.
Addressing the Delayed 3rd Dose Scenario
In your specific case, the infant appears to have received doses at approximately 2,4, and then 15 months (rather than the intended 6 and 12 months). Based on the standard 4-dose schedule:
The 4th dose should still be administered, as the infant has only received 3 doses total when 4 are required for the primary series started before 6 months of age. 1
If the 3rd dose was given at 15 months instead of 6 months, this dose can serve as the 12-month booster dose, and no additional dose is immediately required unless the child remains at high risk. 1
The minimum interval between doses is 8 weeks, so if catch-up vaccination is needed, ensure adequate spacing. 3
Critical Distinction: High-Risk vs. Routine Vaccination
For high-risk infants (those with complement deficiencies, asplenia, or traveling to endemic areas):
- The complete 4-dose series is essential regardless of timing delays. 1
- If doses were missed or delayed, complete the series with appropriate intervals (at least 8 weeks between doses). 3
- Additional booster doses are required: the first booster should be given 3 years after primary series completion, then every 5 years thereafter for children vaccinated before age 7 years. 1, 3
For routine vaccination (not high-risk):
- If the infant received 3 doses with the last at 15 months, this may be considered adequate depending on the specific schedule being followed. 4
- Recent data supports a 1+1 schedule (single dose at 3 months, booster at 12 months) for Nimenrix, which provides robust protection. 4
Common Pitfalls to Avoid
Do not confuse different vaccine schedules: The 4-dose series (2,4,6,12 months) applies specifically to infants starting before 6 months. 1, 2 Infants starting at 7-23 months only need 2 doses. 1
Do not use MenACWY-D (Menactra) in infants with asplenia before age 2 years, as it interferes with pneumococcal conjugate vaccine response. Nimenrix (MenACWY-TT) does not have this restriction. 3, 1
Ensure completion of the primary series before considering booster schedules: The 3-year and 5-year booster recommendations only apply after completing the appropriate primary series for age. 3, 1
Practical Recommendation
Given that the 3rd dose was administered at 15 months (3 months late), and assuming this infant started the series before 6 months of age, no additional immediate dose is required if the infant is not at high risk. 1 The three doses received (at approximately 2,4, and 15 months) provide adequate primary immunization, with the 15-month dose serving as the booster. However, if the infant is at high risk for meningococcal disease, ensure a booster dose is scheduled for 3 years after this final dose. 3, 1