Haemophilus influenzae Type b Meningitis and Invasive Disease

Description

Haemophilus influenzae type b (Hib) causes meningitis and other severe infections (e.g., pneumonia, bacteremia, septic arthritis, and epiglottitis) primarily among infants and children <5 years of age. Because Hib vaccine is used widely in the United States, the highest rate of reported invasive Hib disease is now among infants too young to be fully vaccinated (<6 months of age); the incidence among infants and children 1-4 years of age is much lower than among infants <1 year of age. The disease is uncommon in anyone 5 years of age or older. Most cases occur in infants and children who are unvaccinated or incompletely vaccinated.

Occurrence

In the early 1980s (before licensure of conjugate Hib vaccines), approximately 20,000 cases of invasive Hib disease occurred annually in the United States, primarily among infants and children <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 <200 cases reported annually.

Risk for Travellers

Invasive Hib disease occurs throughout the world. Few countries routinely use Hib vaccine, so invasive Hib disease remains common in infants and young children in many countries, and unvaccinated children who travel may be at risk.

Clinical Presentation

The presentation of Hib disease in children depends on the localization of the infection, which usually occurs after the organism enters the bloodstream from the nasopharynx. Meningitis, pneumonia, sepsis, or arthritis caused by Hib resemble these conditions caused by other bacteria. Epiglottitis presents as sudden onset of fever, drooling, and difficulty in swallowing, and rapidly progresses to airway obstruction.

Prevention

Vaccine

Three conjugate Hib vaccines are licensed for use in infants and children in United States: HbOC (HibTiTER, Wyeth-Lederle), PRP-OMP (PedvaxHIB, Merck & Co., Inc.), and PRP-T (ActHIB, Aventis Pasteur; OmniHIB, GlaxoSmithKline). PRP-OMP vaccine is available combined with hepatitis B vaccine (Comvax). PRP-T (ActHIB) is also available combined with acellular pertussis vaccine (DTaP Tripedia); the combined product is called TriHIBit. TriHIBit is licensed for use only as the fourth dose of the Hib and DTaP series, and should not be given for the first, second, or third doses of the Hib series.

All infants should receive a primary series of conjugate Hib vaccine beginning at age 2 months (Table 8-2).The number of doses in the primary series depends on the type of vaccine used. A primary series of PRP-OMP vaccine is two doses; HbOC and PRP-T require a three-dose primary series (Table 4-3). A booster should be given at age 12-15 months, regardless of which vaccine is used for the primary series.

Table 4-3. Recommended Haemophilus influenzae type b (Hib) routine

Vaccine 2 Months 4 Months 6 Months 12-15 Months
HbOC/PRP-T Dose 1 Dose 2 Dose 3 Booster
PRP-OMP Dose 1 Dose 2 — Booster

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.

Limited data suggest that Hib conjugate vaccines given to infants <6 weeks of age may result in a reduced antibody response to additional doses of Hib vaccine. Therefore, Hib vaccines, including combination vaccines that contain Hib conjugate, should not be given to infants <6 weeks of age.

All three conjugate Hib vaccines licensed for use in infants are interchangeable. 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 type was received in the primary series.

Unvaccinated infants and children ages 7 months and older might not require a full series of three or four doses (Table 8-2). The number of doses an infant or a child needs to complete the series depends on the infant's or child's age and, to a lesser degree, on the number of prior doses of Hib vaccine received. Previously unvaccinated children 15-59 months of age should receive a single dose of any conjugate Hib vaccine. In general, children >59 months of age do not need Hib vaccination. Refer to the American Academy of Paediatrics 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%-30% of recipients and usually resolve within 12-24 hours. Systemic reactions such as fever and irritability are infrequent.

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 TriHIBit and Comvax are the same as those for their individual component vaccines (i.e., DTaP, Hib, and hepatitis B).

Treatment

Specific parenteral antibiotic treatment is necessary for invasive Hib disease, and immediate airway stabilization is necessary for epiglottitis. In certain circumstances, antibiotic prophylaxis is indicated for household contacts. Refer to the American Academy of Paediatrics Red Book for additional information.

Bibliography
  • American Academy of Paediatrics. Haemophilus influenzae Infections. In: Pickering LK, editor. Red Book: 2003 Report of the Committee on Infectious Diseases. 26th ed. Elk Grove Village, IL: American Academy of Paediatrics; 2003:293-301.
  • Wenger JD, Ward JI. Haemophilus influenzae Vaccine. In: Plotkin SA, Orenstein WA, editors. Vaccines. 4th ed. Philadelphia: W.B. Saunders; 2004: 229-68.

- Margaret M. Cortese

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