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Vaccines > Hib
FAQs on Hib Vaccine
Questions and Answers image

Clinical questions & answers 

Related page: Q&As from Providers

General questions:

Vaccine use, recommendations & schedule related:

Combination Vaccines

General questions:
  • What's the difference between Haemophilus influenzae type b and influenza?

Haemophilus influenzae type b is a polysaccharide-
encapsulated bacteria that causes a variety of invasive syndromes, such as meningitis, epiglottitis, and pneumonia. Influenza is a virus that causes the disease influenza. Historical note: Haemophilus influenzae was first isolated in 1889 from the sputum of a patient who died of influenza, and the isolated organism (then called the Pfeiffer bacillus) was assumed to have caused the patient's illness. Haemophilus influenzae received its name in 1920, to acknowledge its historical association with influenza. The viral cause of influenza was not discovered until 1933.


Vaccine use, recommendations and schedule related questions:
  • An infant received 2 doses of Hib vaccine of a type that we do not stock in our clinic. How do I finish the child's Hib series?

Hib conjugate vaccines licensed for use in infants are interchangeable. The series may be completed with any vaccine licensed for infants. The child should receive a total of 3 doses of any combination of Hib vaccines before the first birthday. Any licensed conjugate vaccine may be used as the booster dose at 12-15 months of age if at least two months have elapsed since the previous dose.

  • A 4-year-old received dose #3 of Hib at age 6 months. Does the child need dose #4?

    Yes. All children less than 5 years old need at least one dose of Hib vaccine on or after the first birthday. The last dose should be separated from the previous dose by at least 2 months.

  • How many total doses of Hib vaccine are needed for a 12-month old who received one previous dose?

Children who are not up to date with Hib vaccine present a challenge. They usually don't need a full series of 3 or 4 doses of vaccine (depending on the brand used). A 12-month old who received only one previous dose would need one dose of any conjugate Hib vaccine now, and a second dose 2 months later. AAP's 2000 Red Book contains an excellent Hib vaccination table for children who have fallen behind (p. 271).


  • If a 13-month old received Hib #1 at 8 months of age and Hib #2 today, does s/he still need a booster in 2 months?

ACIP recommendations have not addressed interrupted Hib vaccine schedules. The AAP (2000 AAP Red Book, p. 271) recommends a child in this situation receive one additional dose of any conjugate Hib vaccine 2 months after the dose at 13 months of age.

  • A child started the Hib series at 2 months, received dose #2 at 6 months and dose #3 at 14 months. Does this child need Hib #4?

The child received two doses of Hib before the first birthday and a third dose shortly after the first birthday. According to the 2000 Red Book (table 3.13, p. 271) the child does not need a fourth dose.

  • I've just evaluated a 7-year old who does not have a record of receiving Hib vaccine. Would a dose be indicated now?

ACIP does not recommend routine Hib vaccination of healthy children 59 months of age or older, even if they have no prior history of Hib vaccination.


  • What is the Hib schedule for children >15 months of age who have fallen behind or are completely unvaccinated?

Children 15-59 months of age who have an incomplete Hib vaccination schedule, including those who are unvaccinated, should receive a single dose of any Hib conjugate vaccine. Hib vaccine is not routinely recommended for persons 5 years of age or older.

  • Does anyone 5 years of age or older need to receive Hib vaccine?

There are few data on the efficacy of Hib vaccine in persons 5 years of age or older. ACIP recommends consideration of Hib vaccination for unvaccinated persons 5 years of age and older with anatomic or functional asplenia, sickle-cell anemia, or HIV infection (MMWR 1993;42[RR-4]:8; MMWR 1991;40[RR-12]:29). A single dose of any licensed conjugate vaccine is probably sufficient in most cases (using the dose recommended by the manufacturer for a child). The 2000 AAP Red Book suggests 2 doses separated by 1-2 months for persons with HIV infection or IgG2 immune deficiency.

  • If an infant received one dose of Hib at 5 months, and another at 15 months, does he/she need any more doses?

No. If a child receives a dose of Hib vaccine at 15 months of age or older, he or she does not need any further doses regardless of the number of doses received before 15 months of age.


  • Since the booster dose of Hib vaccine can be given at 12-15 months, is it still necessary to "boost" two months later if the first dose was given at 12-14 months?

If the child received a primary series (2 or 3 doses) of Hib vaccine in the first year of life, then the final (booster) dose of the series may be given as early as 12 months, provided at least 2 months have passed since the last dose. An unvaccinated 12-14 month old child should receive one dose as a primary series, and a booster dose 2 months later. Unvaccinated children 15-59 months of age need only a single dose of any licensed conjugate Hib vaccine.

  • If a dose of Hib vaccine was given by mistake to a 2-week-old, should further doses of Hib vaccine be given?

Limited data suggest that Hib vaccine given before 6 weeks of age may induce immunologic tolerance to Hib antigen and reduce the response to subsequent doses. As a result, Hib vaccine should not be given earlier than 6 weeks of age. However, if a dose was administered before 6 weeks of age, it should not be counted as part of the Hib series. A full series of 4 doses (Hibtiter, ActHib, and Omnihib) or 3 doses (PedvaxHib and Comvax) should be started at 68 weeks of age as usual. No special protocol or testing is recommended for children who received a dose of Hib vaccine before 6 weeks of age.


Combination vaccine related questions:
  • A 12-month-old needs both Hib and hepatitis B vaccines today. Can I use Comvax (Hib-Hep B combination vaccine from Merck), even if the child has not previously received this combination product?

Yes. Comvax can be used when either or both antigens are indicated and neither antigen is contraindicated. Comvax would not be used after the fifth birthday because Hib vaccine is not routinely recommended beyond this age. Comvax should also not be used in infants less than 6 weeks of age.

  • What should we do if we discover a child who has received TriHIBit for the first, second, or third dose of the DTaP-Hib series?

NIP and FDA recommend that any dose of Hib vaccine given as TriHIBit before the first birthday not be counted as part of the Hib series. The child should be revaccinated with Hib vaccine appropriate for his/her age. The DTaP doses do NOT need to be repeated. "Catch-up" schedules for Hib vaccine can be found in the Hib ACIP statement (MMWR 1993;42,RR-13), and in the AAP's 2000 Red Book.

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This page last modified on May 3, 2004
This page last reviewed on January 8, 2002


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