Does a 5-year-old who missed the Haemophilus influenzae type b (Hib) vaccine need to get vaccinated?

Hib Vaccination for a 5-Year-Old Who Missed the Series

A healthy 5-year-old child who missed the Hib vaccine series does not need to receive it now—it is too late, and vaccination is not indicated. 1

Why Vaccination Is Not Needed at Age 5

Previously unvaccinated children aged ≥60 months (5 years and older) who are not considered high-risk generally are immune to Hib disease and do not require catch-up vaccination. 1 This is because:

• By age 3 years (36 months), children have developed natural immunity to Hib through environmental exposure, making additional catch-up doses unnecessary after 15 months of age unless specific high-risk conditions exist 2
• The peak risk for invasive Hib disease occurs in infants and young children, with approximately two-thirds of cases affecting children less than 15 months of age 1
• The risk of invasive Hib disease decreases dramatically after age 5 years in immunocompetent children 1

Age-Based Vaccination Cutoffs

The ACIP provides clear age-based guidance:

• Children aged 15-59 months (up to age 5): Unvaccinated children receiving their first dose need only a single dose of Hib vaccine 2
• Children aged ≥60 months (5 years and older): No vaccination is indicated for healthy children 1

This represents a hard cutoff at the 5th birthday for routine catch-up vaccination.

Important Exception: High-Risk Children

The only 5-year-olds who should receive Hib vaccine are those with specific high-risk conditions. 1 A single dose of any licensed Hib conjugate vaccine should be administered to unimmunized children aged ≥60 months who have:

• Functional or anatomic asplenia (including sickle cell disease or scheduled splenectomy) 1
• HIV infection 1
• Immunoglobulin deficiency (including IgG2 subclass deficiency) 1
• Early component complement deficiency 1
• Recipients of hematopoietic stem cell transplant (who require 3 doses regardless of prior vaccination history) 1
• Those receiving chemotherapy or radiation therapy for malignant neoplasms 1

Clinical Decision Algorithm

For a 5-year-old who missed Hib vaccination:

1. Assess for high-risk conditions listed above 1
2. If healthy (no high-risk conditions): No Hib vaccine needed—document that vaccination is not indicated due to age 1
3. If high-risk condition present: Administer one dose of any licensed Hib conjugate vaccine 1

Common Pitfall to Avoid

Do not attempt to "catch up" the entire Hib series in a healthy 5-year-old. Unlike some other vaccines where completing a series is important regardless of age, Hib vaccine has a specific age cutoff based on the natural acquisition of immunity and the epidemiology of disease 1, 2. Administering unnecessary vaccines wastes resources and exposes the child to needless injections.