Infants and Elderly Most at Risk for Bordetella pertussis

Hospitalization of severe pertussis infections was reported across all age groups, but the youngest and oldest individuals may be the most vulnerable, according to study results published in Clinical Infectious Diseases.

Despite high coverage with pertussis-containing vaccines, Bordetella pertussis incidence in the United States has been increasing. Pertussis symptoms affect individuals of all ages and can range from a relatively mild cold to a severe illness, which may include pneumonia, seizures, respiratory failure, encephalopathy, and/or death. An increasing percentage of older children and adolescents have been infected, which may be due in part to the waning immunity following vaccination with acellular pertussis vaccines, which replaced whole-cell vaccines in the late 1990s. Although the changing epidemiology of pertussis and several factors contributing to its resurgence in the United States have been described, few data exist on the current burden and characteristics of severe disease, especially in age groups outside of infancy. An improved understanding of severe pertussis infections across the lifespan will help guide prevention, control, and treatment options for at-risk individuals. Therefore, this study characterized severe pertussis infections in hospitalized patients of all ages by identifying the risk factors for hospitalization and describing the clinical course and underlying health conditions of hospitalized patients with pertussis.

From 2011 to 2015, cases of pertussis with cough onset in 7 U.S. Emerging Infections Program Network states were reviewed, including Connecticut, Minnesota, New Mexico, Colorado, Georgia, New York, and Oregon. Of 15,942 reported patients with pertussis, 515 (3.2%) were hospitalized and 107 (21.0%) of hospitalized patients required admission to the intensive care unit. Additional information on hospitalized patients was obtained from medical records. Both multivariable and descriptive analyses were conducted to characterize severe pertussis infection and identify potential risk factors.

Study results suggested that individuals at the extreme ends of life may be the most vulnerable to severe pertussis infections; 27% of patients with pertussis aged <1 year and 12% of patients aged ³65 years were hospitalized due to the infection. The highest risk for hospitalization and ICU admission was in infants younger than 2 months and low birth weight was an identified risk factor for hospitalization. In older infants and children up to date on pertussis vaccination, hospitalization risk decreased by 43% (aged 2 to 11 months) and 66% (aged 1 to 10 years). Cough (39.2%), “pertussis” (33.2%), respiratory distress and/or failure (16.1%), bronchiolitis or bronchitis (10.3%), and pneumonia (7.7%) were the most common hospital admission diagnoses. The median length of time from onset to hospitalization was 11 days, which ranged from 7 days (infants aged <2 months) to 17 days (adults aged ³65 years); the median length of hospital stay was 3 days. In addition, several states with the highest incidence had the lowest hospitalization rates, and vice versa, which suggests other factors such as differences in hospitalization practices, thresholds for admission, differences in surveillance systems’ detection of less severe cases, and burden of disease may all contribute.

Overall, the study authors concluded that, “[u]nderstanding the spectrum of severe illness across all age groups is necessary for identifying additional populations at increased risk that could benefit from targeted vaccination or post-exposure prophylaxis.”

Reference

Mbayei SA, Faulkner A, Miner C, et al. Severe pertussis infections in the United States, 2011-2015 [published online October 15, 2018]. Clin Infect Dis. 2018. doi:10.1093/cid/ciy889/5130848