What is the recommended schedule for Haemophilus influenzae type b (Hib) vaccine for children?

Haemophilus influenzae Type b (Hib) Vaccination Schedule for Children

All infants should begin routine Hib vaccination at 2 months of age, with either a 2-dose or 3-dose primary series depending on vaccine type, followed by a booster dose at 12-15 months of age. 1

Primary Vaccination Series (Starting at 2 Months)

The vaccination schedule depends on which Hib conjugate vaccine formulation you use:

For PRP-T Vaccines (ActHib, Pentacel, MenHibRix, or Hiberix)

• 3-dose primary series at 2,4, and 6 months of age 1
• Doses should be administered 8 weeks apart (minimum 4 weeks acceptable if necessary) 1
• First dose can be given as early as 6 weeks of age 1

For PRP-OMP Vaccines (PedvaxHIB or Comvax)

• 2-dose primary series at 2 and 4 months of age 1
• Doses should be administered 8 weeks apart (minimum 4 weeks acceptable if necessary) 1
• A third primary dose is NOT needed if both doses were PRP-OMP 1

Special Consideration for American Indian/Alaska Native Infants

• PRP-OMP vaccines are preferred for AI/AN infants due to substantial protection after the first dose 2
• Either monovalent PRP-OMP (2-dose series) or DTaP-IPV-Hib-HepB/Vaxelis (3-dose series) is recommended 2

Booster Dose (12-15 Months)

• All children need a booster dose at 12-15 months, regardless of which vaccine was used for the primary series 1
• The booster should be given at least 8 weeks after the most recent Hib vaccination 1
• Any licensed Hib conjugate vaccine can be used for the booster, regardless of primary series vaccine 1
• Note: Hiberix should only be used for booster doses (not primary series) in children 12 months through 4 years who received at least 1 prior Hib dose 1

Catch-Up Vaccination Schedules

For Unvaccinated Infants Starting at Age 7-11 Months

• Give 2 doses at least 4 weeks apart 1
• Then give a third (final) dose at 12-15 months or 8 weeks after the second dose, whichever is later 1

For Unvaccinated Children Starting at Age 12-14 Months

• Give 2 doses total, 8 weeks apart 1
• No third dose needed 1

For Unvaccinated Children Starting at Age 15-59 Months

• Only 1 dose needed 1, 3
• No further doses indicated for healthy children 1, 3

For Children Age 5 Years and Older

• No Hib vaccination needed for healthy children 3
• The risk of invasive Hib disease decreases dramatically after age 5 in immunocompetent children 3

High-Risk Children Requiring Additional Doses

Children aged 12-59 months with the following conditions need additional vaccination beyond routine schedules 1:

Conditions Requiring Extra Doses

• Functional or anatomic asplenia (including sickle cell disease) 1, 3
• HIV infection 1, 3
• Immunoglobulin deficiency (including IgG2 subclass deficiency) 1, 3
• Early component complement deficiency 1, 3
• Undergoing chemotherapy or radiation therapy 1, 3

Dosing for High-Risk Children Aged 12-59 Months

• If received 0 or 1 dose before age 12 months: Give 2 doses, 8 weeks apart 1, 3
• If received ≥2 doses before age 12 months: Give 1 dose, 8 weeks after the last dose 1, 3
• If completed primary series and booster at ≥12 months: No additional doses needed 1, 3

Special Circumstances

• Hematopoietic stem cell transplant recipients: 3 doses required regardless of prior vaccination history, beginning 6-12 months after successful transplant, at least 4 weeks apart 1, 3
• Prior to elective splenectomy: Give 1 dose if unimmunized, ideally at least 14 days before the procedure 1, 3

Critical Pitfalls to Avoid

Do not over-vaccinate healthy children: After completing the primary series and booster, healthy children without high-risk conditions need no additional Hib doses, even if they present unvaccinated after 15 months of age (only 1 catch-up dose needed) 3, 4. By age 3 years, children have developed natural immunity to Hib 3.

Do not under-vaccinate high-risk children: Failing to identify conditions like asplenia, HIV, or immunodeficiency leads to inadequate protection in vulnerable populations 3, 4. Always screen for high-risk conditions before determining that no additional doses are needed.

Vaccine interchangeability: If you don't know which Hib vaccine a child previously received, assume a 3-dose primary series is needed to ensure adequate protection 1. However, if PRP-OMP was used for both doses in the primary series, a third primary dose is not indicated 1.