Ask the Experts: Hib (Haemophilus influenzae type b)

Results (29)

Haemophilus influenzae is a bacteria that has encapsulated (typeable) or unencapsulated (nontypeable) strains. Encapsulated strains express one of six antigenically capsular polysaccharides (types a, b, c, d, e, or f). Historically, type b (Hib) was the most common type to cause invasive disease, particularly in young children. H. influenzae colonizes the upper respiratory tract of humans and is transmitted person-to-person by inhalation of respiratory droplets or by direct contact with respiratory tract secretions.

Encapsulated H. influenzae nontype b strains, particularly type a, can cause invasive disease similar to Hib disease. Nontypeable strains also can cause invasive disease but more commonly cause mucosal infections such as otitis media, conjunctivitis, and sinusitis. Vaccines are only available for H. influenzae type b; Hib vaccines do not protect against disease caused by any other H. influenzae strains.

Last reviewed: January 21, 2025

Before 1985, Hib was the leading cause of bacterial meningitis and a common cause of other invasive diseases (such as epiglottitis, pneumonia, septic arthritis, cellulitis, purulent pericarditis, and bacteremia) among U.S. children younger than 5 years of age. An estimated 20,000 cases of invasive Hib disease occurred in this age group each year. Meningitis occurred in approximately two-thirds of children with invasive Hib disease; 15%–30% of survivors had hearing impairment or severe permanent neurologic sequelae. Approximately 3%–6% of all cases were fatal.

Following the licensure of conjugate Hib vaccines in 1987 and 1989, the incidence of Hib disease fell dramatically. During 1989 – 2000, the annual incidence of invasive Hib disease among children younger than 5 years of age decreased by 99%, to less than one case per 100,000 children. Since 2000, the average annual incidence rate of invasive Hib disease among children younger than 5 years of age in the United States remained below the Healthy People 2020 goal of 0.27/100,000 children.

Only 17 confirmed cases of invasive Hib disease among children younger than 5 years were reported in the United States in 2022. The majority of Hib disease in the United States occurs among unimmunized and underimmunized infants and children (those who have an incomplete primary series or are lacking a booster dose) and among infants too young to have completed the primary immunization series.

Last reviewed: January 21, 2025

People with certain immunocompromising conditions are considered at increased risk for invasive Hib disease. These conditions include functional or anatomic asplenia, HIV infection, immunoglobulin (antibody) deficiency including immunoglobulin G2 subclass deficiency, early component complement deficiency, use of a complement inhibitor (such as eculizumab [Soliris], ravulizumab [Ultomiris], or similar), receipt of a hematopoietic stem cell transplant, or receipt of chemotherapy or radiation therapy for treatment of cancer.

Last reviewed: January 21, 2025

Haemophilus influenzae type b is a polysaccharide-encapsulated bacteria that causes a variety of invasive diseases, 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 (viral) influenza disease, and the isolated organism (then called the Pfeiffer bacillus) was incorrectly assumed to have caused the patient’s illness. Haemophilus influenzae received its name in 1920, to acknowledge its historical association with influenza illness. The viral cause of influenza was not discovered until 1933.

Last reviewed: January 21, 2025

The most recent comprehensive Advisory Committee on Immunization Practices (ACIP) recommendations for Hib vaccination were published in 2014 and are available on the CDC website at www.cdc.gov/acip-recs/hcp/vaccine-specific/hib.html. An ACIP update, adding Vaxelis (DTaP-IPV-Hib-HepB, MSP Company) as a preferred Hib-containing option for vaccination of American Indian/Alaska Native children was published in September 2024 and is also available at the link above. Guidance for Hib vaccination is also provided in the annual childhood immunization schedule, available at www.cdc.gov/vaccines/hcp/imz-schedules/child-adolescent-age.html.

Last reviewed: January 21, 2025

Three monovalent Hib vaccines are available in the United States: PedvaxHIB (PRP-OMP, Merck), ActHIB (PRP-T, Sanofi) and Hiberix (PRP-T, GSK). These vaccines are composed of Hib purified polyribosylribitol phosphate (PRP) capsular polysaccharide chemically bound (conjugated) to a protein to enhance the quality of the immune response to PRP. All three vaccines are approved for infants in a 3- or 4-dose series (depending on brand).

Two combination vaccines containing Hib are currently available in the United States: Pentacel (DTaP-IPV/Hib, Sanofi) and Vaxelis (DTaP-IPV-Hib-HepB, MSP Company). Pentacel is licensed for use in children younger than age 5 years and contains Hib conjugate, DTaP, and inactivated polio vaccines; it is approved as a 4-dose series for infants at age 2, 4, 6, and 15 through 18 months, but it is not approved for use as the DTaP/IPV booster dose recommended at age 4 to 6 years. Vaxelis (DTaP-IPV-Hib-HepB) is licensed for use in children younger than age 5 years and is FDA-approved and recommended by CDC as a 3-dose primary series of Hib for infants at age 2, 4, and 6 months. Vaxelis is not approved for use as a Hib booster (4th) dose. Vaxelis contains the same PRP-OMP Hib antigen as PedvaxHIB, but in a reduced amount; like PedvaxHIB, it is an ACIP-preferred option for administration to American Indian and Alaska Native infants (who are at increased risk of early-onset invasive Hib disease) because it induces protective antibody levels after the first dose.

Last reviewed: January 21, 2025

ACIP recommends routine administration of a conjugate Hib vaccine series for all infants beginning at age 2 months. Infants 2 through 6 months of age should receive a 3-dose series of ActHIB, Hiberix, Pentacel, or Vaxelis, or a 2-dose series of PedvaxHIB. The first dose can be administered as early as age 6 weeks, but not earlier. Hib-containing vaccine should not be given before 6 weeks of age. Doses given before 12 months of age should be separated by at least 4 weeks. A booster dose (which will be dose 3 or 4 depending on vaccine type used in primary series) of any Hib-containing vaccine is recommended at age 12 through 15 months and at least 8 weeks after the most recent Hib dose. Vaxelis is recommended only for the primary Hib series and is not recommended for use as a booster (4th) dose. A different Hib-containing vaccine licensed for a booster dose should be used.

Medically stable preterm infants should be vaccinated beginning at age 2 months according to the schedule recommended for other infants, on the basis of chronological age. For special situations in children, refer to the current CDC recommended immunization schedule Hib notes: www.cdc.gov/vaccines/hcp/imz-schedules/child-adolescent-notes.html.

Last reviewed: January 21, 2025

Yes, for the primary series. If either ActHIB (PRP-T), Hiberix (PRP-T), Vaxelis (DTaP-IPV-Hib-HepB), or Pentacel (DTaP-IPV/Hib) is used for a routine primary series dose, a complete routine primary series consists of three doses. PedvaxHIB (PRP-OMP) requires a 2-dose primary series, but if administering a mixed-product primary series including only one dose of PedvaxHIB, a total of 3 doses is needed to complete the primary series.

Vaxelis is not recommended for use as a Hib booster (4th) dose. A different Hib-containing vaccine licensed for the booster dose should be used. If Vaxelis is inadvertently given as the booster dose, the dose does not need to be repeated with another Hib-containing vaccine, if the proper spacing of prior doses is maintained.

Last reviewed: January 21, 2025

Healthcare providers should refer to the catch-up schedule published as part of the CDC Recommended Child and Adolescent Immunization Schedule (available at www.cdc.gov/vaccines/hcp/imz-schedules/child-adolescent-catch-up.html). The catch-up schedule will help determine the number of additional doses needed and the minimum intervals between doses. However, if a healthy child receives a single dose of Hib vaccine at age 15 months or older, he or she does not need any further doses regardless of the number of doses received before age 15 months. Some high-risk children between the age of 15 months and 59 months will be recommended for two doses of Hib vaccine based on previous history of incomplete vaccination; these special situations are reviewed in the Hib notes section of the schedule: www.cdc.gov/vaccines/hcp/imz-schedules/child-adolescent-notes.html.

Last reviewed: January 21, 2025

No. If a healthy 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.

Last reviewed: January 21, 2025

If the child received a primary series (2 or 3 doses, depending upon the product) 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 healthy children 15–59 months of age need only a single dose of any licensed conjugate Hib vaccine. Some high-risk children 15–59 months of age are recommended for two doses of Hib vaccine based on previous history of incomplete vaccination; these special situations are reviewed in the Hib notes section of the schedule: www.cdc.gov/vaccines/hcp/imz-schedules/child-adolescent-notes.html.

Last reviewed: January 21, 2025

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 8 weeks.

Last reviewed: January 21, 2025

Use of DTaP-IPV solution as the diluent for the Hib component is specifically written both on the Pentacel box AND on the DTaP-IPV vial label. The DTaP-IPV component will count as valid doses of DTaP and IPV vaccines, but you should take measures to prevent this error in the future. You cannot mix the Hib component with sterile water. ActHib must ONLY be reconstituted with either the DTaP-IPV solution supplied with Pentacel, or with a specific ActHib saline diluent. If you have a vial of lyophilized ActHib but neither diluent, you must contact the manufacturer (Sanofi) and obtain ActHib diluent.

Last reviewed: January 21, 2025

ACIP does not recommend routine Hib vaccination of healthy children 60 months of age or older, even if they have no prior history of Hib vaccination.

Last reviewed: January 21, 2025

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 3 or 4 doses, depending on the product used, should be started at 2 months 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.

Last reviewed: January 21, 2025

Hib vaccine is not routinely recommended for healthy adults 19 years and older, even if the person did not receive Hib vaccine as a child. However, ACIP recommends that one dose of Hib vaccine should be administered to individuals who have anatomical or functional asplenia or sickle cell disease or are undergoing elective splenectomy if they have not previously received Hib vaccine. Hib vaccine should be administered 14 or more days before splenectomy if possible. Recipients of a hematopoietic stem cell transplant should be vaccinated with a 3-dose series of Hib vaccine 6 to 12 months after a successful transplant, regardless of vaccination history; at least 4 weeks should separate doses. Hib vaccine is not recommended for adults with HIV infection since their risk for Hib disease is low.

Last reviewed: January 21, 2025

When elective splenectomy is planned, vaccination with pneumococcal, meningococcal, and Hib vaccines should precede surgery by at least 2 weeks, if possible. If vaccines are not administered before surgery, they should be administered as soon as the person’s condition stabilizes after surgery.

Last reviewed: January 21, 2025

Pneumococcal conjugate vaccine (PCV), Haemophilus influenzae type b (Hib) vaccine, MenACWY, and meningococcal B vaccine should be given at least 14 days before a scheduled splenectomy, if possible. This is done so the patient is protected from these diseases before the spleen is removed; however, doses given during the 14 days before surgery also can be counted as valid. If the doses cannot be given prior to the splenectomy, they should be given as soon as the patient’s condition has stabilized after surgery. If PCV20 or PCV21 is given, pneumococcal polysaccharide vaccine (PPSV23) is not needed; if PCV15 is given, administer a dose of PPSV23 at least 8 weeks after the dose of PCV15 if the patient is age 2 years or older.

Last reviewed: November 15, 2024

Since the patient is asplenic, the second dose of the primary series of MenACWY should be given at least 8 weeks after the first dose. He will need a dose of MenACWY every 5 years for the rest of his life. The 3-dose series of MenB (whether Trumenba [Pfizer] or Bexsero [GSK]) should be completed. The first booster dose of MenB will be due one year after completion of the primary series and subsequent booster doses are recommended every 2–3 years for the rest of his life. The same MenB vaccine should be used for all doses in the series, including booster doses. People who receive Trumenba brand MenB vaccine have an option to receive MenABCWY (Penbraya, Pfizer) when both MenACWY and MenB vaccines are due at the same visit, as long as doses of Penbraya are spread out by at least 6 months. The patient has already received one dose of PCV20, in accordance with pneumococcal vaccination recommendations for immunocompromised adults younger than age 50, so no further doses are needed. Based on the patient’s age, only one dose of Hib vaccine is recommended, so no further doses are needed. The patient should receive influenza vaccine annually.

Any of these vaccines can be given at the same appointment.

Last reviewed: November 15, 2024

You are interpreting the recommendations correctly, and age is an important factor in this issue. The recommendation for Hib vaccination for asplenia applies to people of all ages. Only children ages 12 through 59 months are subject to the recommendation for Hib vaccination for immunoglobulin deficiency or early component complement deficiency or use of a complement inhibitor (such as eculizumab [Soliris], or a related product).

Last reviewed: January 21, 2025

Yes. If different brands of Hib vaccine are given at 2 and 4 months of age then the child should receive a third primary dose of either vaccine at 6 months of age. A 2-dose primary schedule (that is, doses at age 2 and 4 months) is only appropriate when both doses are PedvaxHIB.

Last reviewed: January 21, 2025

Hib invasive disease does not always result in development of protective antibody levels. Children younger than 24 months of age who develop invasive Hib disease should be considered susceptible and should receive Hib vaccine. Vaccination of these children should start as soon as possible during the convalescent phase of the illness. A complete series as recommended for the child’s age should be administered.

Last reviewed: January 21, 2025

Hib meningitis incidence historically peaked at a younger age (4–6 months) among AI/AN infants than among other U.S. infant populations (6–7 months). ACIP has made a preferential recommendation for vaccination with a primary series of PedvaxHIB (PRP-OMP, Merck) or Vaxelis (DTaP-IPV-Hib-HepB, MSP Company) for AI/AN infants. PedvaxHIB and Vaxelis (which also contains PRP-OMP as its Hib component) both produce a protective antibody response after the first dose.

Last reviewed: January 21, 2025

All Hib-containing vaccines should be administered by the intramuscular route.

Last reviewed: January 21, 2025

The third dose of Vaxelis (DTaP-IPV-Hib-HepB, MSP Company) administered at age 5 months (less than 24 weeks of age) is not considered a valid dose of the HepB component, because the last dose of HepB vaccine should be given at 24 weeks of age or older. The child will need an additional dose of HepB vaccine at age 24 weeks or older, and at least 4 weeks after the inadvertent dose of Vaxelis. The DTaP, IPV, and Hib components of the Vaxelis dose erroneously administered at age 5 months are considered valid doses and do not need to be repeated, as long as there was a minimum 4-week interval between the second and third doses of these three components.

Last reviewed: January 21, 2025

Hib vaccination is contraindicated for individuals known to have experienced a severe allergic reaction (anaphylaxis) to a vaccine component or following a prior dose. Hib-containing vaccines are contraindicated for children younger than 6 weeks of age because of the potential for development of immunologic tolerance. The PedvaxHIB vial stopper contains dry natural rubber which could produce an allergic reaction in children with severe allergy to latex.

Vaccination should be delayed for children with moderate or severe acute illnesses. Minor illnesses, such as a mild upper respiratory infection are not a reason to delay vaccination.

Contraindications and precautions for the use of Pentacel (DTaP-IPV/Hib) and Vaxelis (DTaP-IPV-Hib-HepB) are the same as those for their individual component vaccines.

Last reviewed: January 21, 2025

There is an extremely rare risk of an unpredictable, serious allergic reaction (anaphylaxis) following administration of any vaccine. Most people have no side effects from Hib vaccination. Some experience fever or a mild reaction at the injection site, including redness, warmth, tenderness, or swelling. These side effects resolve without treatment within a day or two after vaccination.

All serious adverse events that occur after receipt of any vaccine should be reported to the Vaccine Adverse Event Reporting System (VAERS) (https://vaers.hhs.gov).

Last reviewed: January 21, 2025

Hib vaccine should be maintained at refrigerator temperature between 2°C and 8°C (36°F and 46°F). Manufacturer package inserts contain additional information and can be found at  www.immunize.org/official-guidance/fda/pkg-inserts/. For complete information on best practices and recommendations please refer to CDC’s Vaccine Storage and Handling Toolkit available at this website: www.cdc.gov/vaccines/hcp/storage-handling/index.html.

Last reviewed: January 21, 2025

CDC published its current guidance for chemoprophylaxis of close contacts of a patient with invasive Hib disease on page 10 of its February 28, 2014, MMWR, “Prevention and Control of Haemophilus influenzae Type b Disease: Recommendations of the Advisory Committee on Immunization Practices (ACIP)”, available at: www.cdc.gov/mmwr/PDF/rr/rr6301.pdf.

According to the MMWR, secondary cases of Hib disease (illness occurring within 60 days of contact with a patient) occur but are rare. Secondary attack rates are higher among household contacts younger than 48 months (2.1%), especially those younger than 12 months (6%) and younger than 24 months (3%). Data are conflicting on the risk for secondary illness among childcare contacts, but it is thought to be lower than among household contacts. Rifampin is recommended for chemoprophylaxis because it achieves high concentrations in respiratory secretions and eradicates nasopharyngeal carriage in more than 95% of carriers.

Index patients who are treated with an antibiotic other than cefotaxime or ceftriaxone and are younger than 2 years of age should receive rifampin prior to hospital discharge. Because cefotaxime and ceftriaxone eradicate Hib colonization, prophylaxis is not needed for patients treated with either of these antibiotics.

Rifampin chemoprophylaxis is recommended for all household contacts in households with members younger than 4 years who are not fully vaccinated, households with a child younger than 12 months who has not completed the primary Hib series, or households with a contact who is an immunocompromised child regardless of that child’s vaccination status.

Rifampin chemoprophylaxis is recommended in childcare settings when two or more cases of invasive Hib disease have occurred within 60 days and unimmunized or underimmunized children attend the facility. When prophylaxis is indicated, it should be prescribed for all attendees, regardless of age or vaccine status, and for childcare providers. Refer to the current AAP Red Book chapter on Haemophilus influenzae infections for more information on this issue and consult with local or state public health for guidance.

There are no guidelines for control measures around cases of invasive non-type b H. influenzae disease at this time. Chemoprophylaxis is not recommended for contacts of persons with invasive disease caused by non-type b H. influenzae although a small number of secondary cases have been documented. Information about secondary cases of non-type b H. influenzae invasive disease is available in this 2023 MMWR, entitled “Secondary Cases of Invasive Disease Caused by Encapsulated and Nontypeable Haemophilus influenzae — 10 U.S. Jurisdictions, 2011–2018”, available at www.cdc.gov/mmwr/volumes/72/wr/pdfs/mm7215a2-H.pdf.

Last reviewed: January 21, 2025

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