Analysis of infant pertussis hospitalizations in Michigan, 2008-2010

Introduction: Infants are at highest risk of morbidity and mortality from pertussis, particularly before their first vaccine dose at 2 months. According to the 2011 National Health Interview Survey (NHIS), 13.8% of White adults (95% CI: 12.9-14.7) and 11.0% of Black adults (95% CI: 9.5-12.6) reported being vaccinated against pertussis within the last 6 years. With infants most often contracting pertussis from unvaccinated household members, disparities in adult vaccination rates may partially explain disparities in infant pertussis rates.

Materials/Methods: The Michigan Inpatient Database contains all discharge records from Michigan short-stay hospitals. Using data from 2008 to 2010, we analyzed infant (< 1 year) pertussis hospitalizations by race. Infant hospitalizations for delivery were excluded.

Results: Between 2008 and 2010, there were 36,085 infant hospitalizations in Michigan; 177 had a primary diagnosis of pertussis. White and Black infants had 4.43 and 7.42 pertussis hospitalizations per 10,000 infants, respectively. The median age at hospitalization was 2.5 months for White infants and 2.0 months for Black infants.

Discussion: Initial results indicate higher rates of pertussis hospitalization and a lower median age among Black infants. Vaccination of pregnant women is an effective strategy to prevent infant pertussis. This leads to transferal of maternal antibodies in utero and offers protection until the infant is vaccinated. Future analyses will use claims data to examine pertussis vaccination among pregnant women in Michigan, with a focus on disparities.