eMedicine Specialties > Infectious Diseases > Bacterial Infections

Haemophilus Influenzae Infections: Follow-up

Author: Vidya R Devarajan, MD,
Contributor Information and Disclosures

Updated: Aug 12, 2008

Follow-up

Further Inpatient Care

• Index patients younger than 2 years who will be in contact with unvaccinated or incompletely immunized children younger than 4 years and who were treated with a regimen other than cefotaxime of ceftriaxone should be treated with rifampin before or at discharge from the hospital because other antibiotics used for the treatment of H influenzae type b (Hib) meningitis do not reliably eradicate Hib from the nasopharynx. Treatment with cefotaxime and ceftriaxone eradicates Hib colonization and therefore eliminates the need for chemoprophylaxis of the index patient.
• Search for secondary foci of infection, such as septic arthritis, if patients have prolonged fever during treatment of meningitis.
• Droplet precautions should be followed for the first 24 hours following the initiation of appropriate therapy in patients with invasive Hib disease.¹⁴

Further Outpatient Care

• Unvaccinated or undervaccinated children younger than 4 years who have household contact with an index patient have a 600-fold increased risk of Hib disease.
• Begin chemoprophylaxis as soon as possible because the risk of secondary disease is greatest within a few days after disease onset in the index case. Rifampin is the drug of choice for chemoprophylaxis because it achieves high bactericidal concentrations intracellularly and in mucosal secretions, thereby eradicating 95% of Hib from the nasopharynx. Administer rifampin to all household contacts, including adults, children, and the index patient, if a close household contact is immunocompromised, regardless of immunization status; younger than 48 months and is not completely immunized or unimmunized; or younger than 12 months and has not received the 2- to 3-dose primary series.  Chemoprophylaxis is not needed in contacts of patients with non-Hib invasive disease.¹⁴
• Full immunization is defined as having received at least one of the following:¹⁴
  • One dose of a Hib conjugate vaccine when at age 15 months or older
  • Two doses at age 12-14 months
  • Two or more doses at age 12 months or older
  • Three doses before age 12 months, with a booster dose at age 12 months or older
• If the close contact group includes a fully vaccinated child who is immunocompromised, then make an exception because the vaccination may have been ineffective. A close contact group is defined as persons who reside with the patient or a nonresident who has spent 4 hours or more with the index patient for at least 5 of the 7 days preceding the day of hospitalization of the patient.¹⁴
  • Administer rifampin within 7 days after hospitalization of the index patient to ensure effectiveness.
  • The need for chemoprophylaxis has decreased dramatically because the Hib conjugate vaccine now protects many children.
• The need for all daycare center contacts to be treated is debatable when a single case has occurred because of uncertainty about the actual risk of secondary Hib disease in this setting.¹⁴
  • If 2 or more cases of Hib disease have occurred in a childcare center within 60 days, the consensus is to institute prophylaxis to all attendees and staff members.
  • Pharyngeal cultures do not need to be obtained to determine prophylaxis, as this delays administration of rifampin.
  • Administer H influenzae conjugate vaccine to patients younger than 24 months with invasive Hib disease during convalescence regardless of prior immunization. Patients aged 24 months or older with invasive Hib disease do not need immunization.
  • Patients with recurrent invasive Hib disease despite receiving Hib immunization should undergo immunologic evaluation.

Inpatient & Outpatient Medications

• If the patient has significantly improved clinically, oral antibiotics may follow parenteral antibiotics started in the hospital to finish the course of treatment.
• Adjust antibiotics based on susceptibilities of the involved organism.

Deterrence/Prevention

• The highly effective Hib conjugate vaccine, now routinely administered to infants and children, has dramatically reduced the prevalence of invasive Hib disease. The vaccine elicits a protective antibody and prevents disease by reducing pharyngeal colonization with Hib. Presently, no vaccines prevent disease caused by NTHi .
• The first Hib vaccine was an unconjugated polysaccharide vaccine composed of the purified PRP capsular polysaccharide. This vaccine induced an ambiguous immune response, did not provide complete protection in children, and provided no antibody protection in infants. This led to the development of the conjugate vaccines in which PRP is covalently linked to a protein.
• Currently, 3 licensed vaccines are available. They differ in the protein carrier used, the molecular size of the saccharide, and the method of conjugating the protein to the saccharide. These include HibTITER (HbOC [mutant diphtheria toxin as the carrier protein]), PedvaxHIB (PRP-OMP [major outer membrane protein of N meningitidis serogroup B as the carrier protein]), and ActHIB/OmniHIB (PRP-T [tetanus toxoid as the carrier protein]).¹⁴
• PRP-OMP induces a good immune response after a single dose in infants, but antibody levels after 3 doses are lower than those induced by HbOC and PRP-T.
• The PRP-OMP vaccine is therefore recommended in American Indians and Alaska native children because of a rapid seroconversion of protective antibodies with the PRP-OMP vaccine.
• The vaccines are well tolerated, with occasional redness and swelling at the site of vaccination (10-15% of infants), more commonly after the initial dose than after subsequent injections.
• The estimated effectiveness of the vaccine in children younger than 5 years is 98%.
• The combination of Hib conjugate vaccine (PRP-OMP) with hepatitis B vaccine (Recombivax HB) is licensed for use at age 2 months, 4 months, and 12-15 months. The DTaP-Hib is another combination vaccine that is licensed for use but only as a fourth dose in the DTaP and Hib series.¹⁴
• Administer routine immunization of the Hib conjugate vaccine in all infants and children.
• In the primary series, administer a 3-dose regimen of HbOC or PRP-T or a 2-dose regimen of PRP-OMP at 2-months intervals, beginning at age 2 months. Any conjugate Hib vaccine can serve as the booster immunization given in children aged 12-15 months. Lack of the booster dose in the United Kingdom might be a reason for the recent increase in Hib disease since the Hib vaccine was introduced there in 1992.
• Children with decreased or absent splenic function who have received their full immunization series need not be immunized further.
• Children who have received the primary series and a booster dose and are undergoing scheduled splenectomy (eg, for Hodgkin disease, spherocytosis) may benefit from an additional dose of any licensed conjugate vaccine given 7-10 days before the procedure.
• Unimmunized children older than 59 months with an underlying disease may be immunized with 2 doses of vaccine 2 months apart.

Complications

• Complications of meningitis include seizures, cerebral edema, subdural effusion or empyema, inappropriate secretion of antidiuretic hormone syndrome, cortical infarction, cerebritis, intracerebral abscess, hydrocephalus, and cerebral herniation. Protracted fever is not uncommon, with approximately 10% of children remaining febrile for at least 10 days.
• Complications of orbital cellulitis include subperiosteal or orbital abscesses.
• Complications of pneumonia include empyema and pericarditis.
• Complications of otitis and sinusitis include mastoiditis and parameningeal abscess.

Prognosis

• The prognosis of meningitis depends on age at presentation, duration of illness prior to antimicrobial therapy, CSF capsular polysaccharide concentration, and the rapidity with which it is cleared from the CSF, blood, and urine. Dexamethasone administered concurrently or shortly before the initial administration of antibiotics decreases the likelihood of hearing loss associated with Hib meningitis.
• The prognosis of uncomplicated Hib pneumonia and nonencapsulated H influenzae infections is usually good.

Patient Education

• Alert parents and caregivers of the index patient that if any exposure to the index patient has occurred within a childcare setting to seek prompt medical care for any signs or symptoms that may be related to Hib infection.
• For excellent patient education resources, visit eMedicine's Blood and Lymphatic System Center and Cold and Flu Center. Also, see eMedicine's patient education articles Sepsis (Blood Infection); Immunization Schedule, Children; and Flu in Children.

Miscellaneous

Medicolegal Pitfalls

• H influenzae type b (Hib) resistance to several antibiotics, including ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, rifampin, and some second-generation cephalosporins, has increased worldwide. When choosing an antibiotic, consider the local antibiotic susceptibility patterns of invasive isolates.
• The treatment of Hib bacteremia and its invasive disease should include penetration of the blood-brain barrier (since occult CNS disease must be considered in any Hib infection), achievement of bactericidal titers, and an adequate duration of therapy to sterilize primary and potential secondary foci.
• The nasopharyngeal carriage rate of NTHi is high; therefore, a positive culture result is not helpful and should not be used to confirm a diagnosis of H influenzae disease.
• If epiglottitis is suspected, securing an airway prior to doing anything that might make the patient more anxious is crucial.

Special Concerns

• Recent genetic studies have revealed that the bacterium formerly known as H aegyptius belongs to the H influenzae species. It causes conjunctivitis and a fulminant invasive disease called Brazilian purpuric fever, called so because it was observed in Brazil in children aged 1-4 years who presented with high fever, vomiting, abdominal pain, petechiae, purpura, peripheral necrosis, and vascular collapse. The mortality rate may approach 70%.

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