Haemophilus Influenzae Type b Meningitis
Description
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Haemophilus influenzae type b (Hib) causes meningitis and other severe bacterial infections (for example, pneumonia, septic arthritis, epiglottitis, and sepsis), primarily among infants and children younger than 5 years of age. Because the Hib vaccine is used widely in the United States, the highest rate of reported invasive Hib disease is among infants younger than 6 months of age; the incidence among infants and children 1 through 4 years of age is much lower than among infants younger than 1 year of age. The disease is rarely reported in anyone 5 years of age or older. Most cases occur in infants and children who are unvaccinated or incompletely vaccinated.
In the early 1980s (before licensure of conjugate Hib vaccines), it was estimated that about 20,000 cases of invasive Hib disease occurred annually in the United States, primarily among infants and children younger than 5 years of age. As a result of the widespread use of conjugate Hib vaccines, the disease is now uncommon in the United States, with fewer than 200 cases reported annually.
Risk for Travelers
Invasive Hib disease occurs throughout the world. Few countries routinely use Hib vaccine, so invasive Hib disease remains common in many countries.
Preventive Measures
Vaccine
Three different conjugate Hib vaccines are licensed for use in infants: HbOC (HibTiTER®, Wyeth-Lederle), PRP-OMP (PedvaxHIB®, Merck & Co., Inc.), and PRP-T (ActHIB®, Aventis Pasteur, and OmniHIB®, GlaxoSmithKline). A fourth Hib conjugate vaccine, PRP-D (ProHIBIT®, Aventis Pasteur), is licensed only for infants and children 12 through 60 months of age and should not be used for the primary series. PRP-OMP vaccine is available combined with hepatitis B vaccine (Comvax®). HbOC and PRP-T are also available combined with whole-cell pertussis vaccine
Table 3-3.--Recommended Haemophilus influenzae Type b (Hib) Routine Vaccination Schedule. Vaccine 2 Months 4 Months 6 Months 12 to 15 Months
HbOC/PRP-T Dose 1 Dose 2 Dose 3 Booster
PRP-OMP Dose 1 Dose 2 ---------------- Booster
PRP-D* ---------------- ---------------- ---------------- Single dose*
* PRP-D is licensed for a booster dose following a primary series of another type of vaccine when the infant is 12 months of age and for a single dose in previously unvaccinated infants at 15 months of age.
(Tetramune and ActHIB®/DTP, respectively). PRP-T (ActHIB®) is also available combined with acellular pertussis vaccine (DTaP Tripedia®) (the combined product is called TriHIBit). However, since February 1999, TriHIBit has been licensed for use only as the fourth dose of the Hib and DTaP series. It should not be given for the first, second, or third doses of the Hib series.
All infants, including those born prematurely, should receive a primary series of conjugate Hib vaccine (separate or as a combination vaccine), beginning at 2 months of age. The number of doses in the primary series depends on the type of vaccine used. A primary series of PRP-OMP (PedvaxHIB®) vaccine is two doses; HbOC (HibTiTER®) and PRP-T (ActHIB® and OmniHIB®) require a three-dose primary series (see Table 3-3). A booster should be given at 12 to 15 months of age, regardless of which vaccine is used for the primary series.
The optimal interval between doses is 2 months, with a minimum interval of 1 month. At least 2 months should separate the booster dose from the previous (second or third) dose. Hib vaccines may be given simultaneously with all other vaccines.
Data suggest that if Hib conjugate vaccines are given to infants younger than 6 weeks of age, they can induce immunologic tolerance to additional doses of Hib vaccine. Therefore, Hib vaccines, including combination vaccines that contain Hib conjugate, should never be given to a child younger than 6 weeks of age.
All three conjugate Hib vaccines licensed for use in infants are interchangeable. A series that includes vaccines of more than one type will induce a protective antibody level. If it is necessary to change the type of vaccine, three doses of any combination constitute the primary series. Any licensed conjugate vaccine may be used for the booster dose, regardless of what was received in the primary series.
Unvaccinated infants and children 7 months of age or older might not require a full series of three or four doses. The number of doses an infant or a child needs to complete the series depends primarily on the infant's or child's age at the time and, to a lesser degree, on the number of prior doses of Hib vaccine received. Previously unvaccinated infants and children 15 through 60 months of age should receive a single dose of any conjugate Hib vaccine. In general, children older than 60 months of age do not need Hib vaccination. Refer to the American Academy of Pediatrics Red Book for additional information on late or lapsed Hib vaccination schedules.
Adverse Reactions
Adverse events following vaccination with Hib conjugates are uncommon. Swelling, redness, or pain, or a combination of these, have been reported in 5% to 30% of recipients and usually resolve within 12 to 24 hours. Systemic reactions such as fever and irritability are infrequent. Information on adverse events suggests that the risks for local and systemic events following Tetramune and ActHIB®/DTP administration are similar to those following concurrent administration of their individual component vaccines and are probably due to the pertussis component of the DTP vaccine.
Precautions and Contraindications
Vaccination with Hib conjugate vaccine is contraindicated in anyone known to have experienced anaphylaxis following a prior dose of that vaccine. Vaccination should be delayed in infants and children with moderate or severe acute illnesses. Minor illnesses (for example, mild upper respiratory infection) are not contraindications to vaccination. Contraindications and precautions for the use of Tetramune, ActHIB®/DTP, TriHIBit, and Comvax® are the same as those for their individual component vaccines (that is, DTP, DTaP, Hib, and hepatitis B).
Credits: National Center for Infectious Diseases
