| Haemophilus influenzae type b (Hib) |
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| Disease Issues |
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| What is
Haemophilus influenzae? |
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| 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. |
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| Encapsulated H.
influenzae nontype b strains, particularly
type a, can cause invasive disease similar to
Hib disease (see next question). 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 only protect against H. influenzae
type b strains. |
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| How common is
Haemophilus influenzae type b (Hib) disease? |
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| 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
4% of all cases were fatal. |
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| 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. |
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| Only 14 cases of
invasive Hib disease among children younger
than 5 years were reported in 2019. 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. |
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| What are the
risk factors for invasive Hib disease? |
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| Persons with
certain immunocompromising conditions are
considered at increased risk for invasive Hib
disease. These conditions include functional
or
anatomic asplenia, HIV infection,
immunoglobulin deficiency including immunoglobulin G2 subclass deficiency, early
component complement deficiency,
receipt of a hematopoietic stem cell
transplant, or receipt of chemotherapy or
radiation therapy for treatment of cancer. |
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| What's the
difference between Haemophilus influenzae type
b and influenza? |
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| 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. |
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| 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. |
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| Where can I
find the most recent recommendations for Hib
vaccines? |
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| The most recent
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/mmwr/pdf/rr/rr6301.pdf.
Guidance for Hib vaccination is also provided
in the annual childhood immunization schedule,
available at
www.cdc.gov/vaccines/schedules/hcp/child-adolescent.html. |
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| What Hib
vaccines are available in the United States? |
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| Three monovalent
Hib vaccines are available in the United
States: PedvaxHIB (PRP-OMP, Merck), ActHIB (PRP-T,
Sanofi Pasteur) and Hiberix (PRP-T,
GlaxoSmithKline). 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). |
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| One combination
vaccine containing Hib is currently available
in the United States. Pentacel (DTaP-IPV/Hib,
Sanofi Pasteur) contains Hib conjugate, DTaP
and inactivated polio vaccines and is approved
for infants at age 2, 4, 6, and 15 through 18
months of age. It is not approved for the
DTaP/IPV booster dose at age 4 through 6
years. Vaxelis (DTaP-IPV-Hib-HepB, MCM
Company) is licensed and recommended by the
ACIP for the primary series of Hib in infants
at age 2, 4, and 6 months, but is not expected
to become commercially available until
sometime in 2021. Vaxelis contains the same
PRP-OMP Hib antigen as PedvaxHIB, but in a
reduced amount. |
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| What are the
recommendations for Hib vaccination in the
United States? |
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| The 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. 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. |
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| 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. Unimmunized children 60
months and older who have HIV infection should
receive 1 dose of Hib vaccine. |
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| Can all of the
licensed Hib-containing vaccines be used
interchangeably? |
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| Yes. If either
ActHIB, Vaxelis, Pentacel, or Hiberix is used
for a routine primary series dose, a complete
routine primary series consists of three
doses. |
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| What is the
Hib vaccine schedule for children who have
fallen behind or are completely unvaccinated? |
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| Healthcare
providers should refer to the catch-up
schedule which is approved and published each
year by the ACIP, AAP, and AAFP (available at
www.cdc.gov/vaccines/schedules/hcp/child-adolescent.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 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. Some
high-risk children between the ages of 15
months and 59
months will be recommended for two doses of
Hib vaccine based on previous history of
incomplete vaccination. |
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| If a healthy
infant received one dose of Hib at 5 months,
and another at 15 months, does he/she need any more doses? |
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| 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. |
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| 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? |
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| 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 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. |
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| A 4-year-old
received dose #3 of Hib at age 6 months. Does
the child need dose #4? |
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| 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. |
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| I've just
evaluated a 7-year old who does not have a
record of receiving Hib vaccine. Would a dose
be indicated now? |
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| 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. |
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| If a dose of
Hib vaccine was given by mistake to a
2-week-old, should further doses of Hib
vaccine be given? |
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| 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. |
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| Which adults
should receive Hib vaccine? |
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| 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 persons 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. |
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| When should
Hib vaccine be administered to a person having
a splenectomy? |
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| 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. |
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| Should adult
patients who are not asplenic but who have
hypogammaglobulinemia receive Hib vaccine? The
2014 Hib ACIP statement includes
immunoglobulin deficiency in its "high-risk
groups" for Hib disease, but the
recommendations seem to imply that Hib vaccine
is not necessarily for adults
with immunoglobulin deficiency whose spleen is
intact. Am I interpreting ACIP correctly on
this matter? |
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| You are
interpreting the recommendations correctly,
and age is an important factor in this issue.
The recommendation for Hib vaccination for
asplenia
applies to persons of all ages. The
recommendation for Hib vaccination for
immunoglobulin deficiency applies only to
children 12 through 59 months of
age. |
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| If a child
receives a different brands of Hib vaccine at
2 and 4 months of age should a dose also be
given at 6 months of age? |
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| 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. |
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| Should
children who recover from invasive Hib disease
be vaccinated? |
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| 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. |
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| Are there any
special Hib vaccination recommendations for
American Indian/Alaska Native (AI/AN) children? |
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| 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).
Vaccination with a 2-dose primary series of PedvaxHIB is preferred for AI/AN infants to
provide early protection because this vaccine
produces a
protective antibody response after the first
dose. |
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| How should Hib
vaccines be administered? |
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| All
Hib-containing vaccines should be administered
by the intramuscular route. |
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| We
inadvertently gave a child only the DTaP-IPV
component of Pentacel not realizing that this
component was intended to reconstitute the Hib
component.
Does this count as a valid dose of DTaP and
IPV? Can we mix the unused Hib component with
sterile water and give it separately? |
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| 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 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 ActHIB but neither
diluent, you must contact the manufacturer
(Sanofi) and obtain ActHIB diluent. |
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| What are the
contraindications and precautions for Hib
vaccine? |
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| Vaccination with
Hib vaccine is contraindicated for persons
known to have experienced a severe allergic
reaction (anaphylaxis) to a vaccine component
or
following a prior dose. 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 contraindications to vaccination. Hib
conjugate vaccines are contraindicated for
children younger than 6 weeks of age because
of the potential for
development of immunologic tolerance.
Contraindications and precautions for the use
of Pentacel (DTaP-IPV/Hib) and Vaxelis
(DTaP-Hib-HepB-IPV) are
the same as those for their individual
component vaccines. |
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| What adverse
reactions may occur after Hib vaccination? |
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| Adverse reactions
following Hib conjugate vaccines are not
common. Swelling, redness, or pain have been reported in 5%–30% of recipients and usually
resolve within 12–24 hours. Systemic reactions
such as fever and irritability are infrequent.
Serious reactions are rare. |
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| All serious
adverse events that occur after receipt of any
vaccine should be reported to the Vaccine
Adverse Event Reporting System (VAERS)
(vaers.hhs.gov). |
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| How should Hib
vaccines be stored? |
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| 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/packageinserts. For complete
information on best practices and
recommendations please refer to
CDC's Vaccine Storage and Handling Toolkit at
www.cdc.gov/vaccines/hcp/admin/storage/toolkit/storage-handling-toolkit-2020.pdf. |
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| Should close
contacts of a patient with invasive Hib
disease receive antibiotic prophylaxis? |
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| 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 child care 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. |
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| 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. |
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| 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. |
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| Rifampin
chemoprophylaxis is recommended in child care
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 child care providers.
See the current AAP Red Book chapter on
Haemophilus influenzae infections for more information on this
issue. |
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| There are no
guidelines for control measures around cases
of invasive nontype b H. influenzae disease. Chemoprophylaxis is not recommended for
contacts of persons with invasive disease
caused by nontype b H. influenzae because
cases of secondary transmission of disease
have not been
documented. |
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ACIP Recommendations
Vaccine Information Statements 
