Pertussis Infections in Hospitalized Patients – United States, 2010-2014

Background: Since the mid-2000s, incidence of pertussis has increased in the United States. While infants remain at the greatest risk for illness and death from pertussis, the epidemiology of pertussis is evolving, with more adolescents and adults are becoming infected. An improved understanding of severe pertussis infection among all age groups will help guide prevention, control and treatment options for those at risk of complications and death from pertussis.

Methods: All hospitalized case-patients with confirmed or probable pertussis from January 1, 2010 – December 31, 2014 were identified in the 7 US states participating in the Enhanced Pertussis Surveillance network. Chart reviews were conducted using a standardized case report form and descriptive analyses were conducted using SAS 9.3.

Results: Among the 464 hospitalized case-patients identified, 238 (51.3%) were aged <4 months and 102 (22.0%) were aged >21 years. Of the 226 case-patients aged ≥4 months, only 31.9% were up-to-date on pertussis-containing vaccines. On past medical history, 165 (35.6%) reported at least one underlying condition, with higher rates reported among adults aged ≥21 years (89.2%), including a substantial proportion (31.4%) with a history of asthma and/or chronic obstructive pulmonary disease (COPD). The median length of hospital stay was 3 days, and was longest in infants aged <4 months of age at 4.5 days. A total of 100 case-patients (21.6%) required intensive care, with the highest rates among infants aged <4 months (32.4%), and 19 (8.0%) requiring mechanical ventilation. One infant aged <2 months required exchange transfusion and another required extracorporeal membrane oxygenation. Two deaths were observed, including an infant aged 42 days and an adult aged 76 years, both due to respiratory failure.

Conclusion: Infants <4 months of age accounted for the majority of hospitalized pertussis cases and experienced the greatest disease severity in terms of required clinical interventions and length of hospitalization. However, adults also experienced severe pertussis infections, and the high rates of obstructive pulmonary disease such as asthma or COPD suggest a potential risk factor for severe pertussis infection requiring hospitalization.