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Haemophilus influenzae type b infection, vaccination, and H. influenzae carriage in children in Minnesota, 2008-2009

S A Lowther1, N Shinoda, B A Juni

  • 1Epidemic Intelligence Service, Division of Applied Sciences, Scientific Education and Professional Development Program Office, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. sgl6@cdc.gov

Epidemiology and Infection
|June 17, 2011
PubMed

Insights

Haemophilus influenzae type b (Hib) vaccine deferrals in 2008 led to increased invasive Hib cases in Minnesota. While Hib carriage was not widespread in children surveyed in 2009, unvaccinated children remain at risk.

Area of Science:

  • Pediatrics
  • Infectious Diseases
  • Vaccinology

Background:

  • An increase in invasive Haemophilus influenzae type b (Hib) cases, including one death, was observed in Minnesota in 2008.
  • This surge followed a recommended deferral of Hib vaccine boosters due to a national vaccine shortage.
  • Several affected children had incomplete Hib vaccination histories, with some refusals or delays, and one had an immunodeficiency.

Purpose of the Study:

  • To evaluate Haemophilus influenzae type b (Hib) carriage and vaccination status in young children following an increase in invasive Hib disease.
  • To identify risk factors associated with Hib carriage and compare vaccination completion rates for Hib, diphtheria-tetanus-acellular pertussis (DTaP), and pneumococcal conjugate vaccine (PCV-7).

Main Methods:

  • A survey was conducted in 18 clinics in Minnesota between February and March 2009, targeting children aged 4 weeks to 60 months for pharyngeal Hib carriage.
  • Vaccination records for Hib, DTaP, and PCV-7 were compared, and parents completed questionnaires on carriage risk factors and vaccination beliefs.
  • Nasopharyngeal swabs were collected from 1631 children to detect Hib carriage.

Main Results:

  • No Haemophilus influenzae type b (Hib) carriage was detected in the 1631 children surveyed.
  • Hib vaccination completion was less frequent compared to diphtheria-tetanus-acellular pertussis (DTaP) and pneumococcal conjugate vaccine (PCV-7).
  • Non-type b H. influenzae was detected in 15% of children, associated with male sex, older age (24-60 months), extensive daycare attendance, household smoking, and Asian/Pacific Islander ethnicity.

Conclusions:

  • Despite the absence of widespread Hib carriage in young children in 2009, invasive Hib disease cases continued to occur, caused by the same strain circulating in 2008.
  • Haemophilus influenzae type b (Hib) remains a significant risk for vulnerable and unvaccinated children.
  • Maintaining high vaccination coverage is crucial to prevent resurgence of invasive Hib disease.

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