PIN10 - Recent Trends In Incidence Of Infant Pertussis Hospitalizations In The United States

Abstract

Infants are at greatest risk for severe pertussis (~50% of infant cases require hospitalization). Recent surveillance indicates a resurgence of overall pertussis incidence in the US, but limited data exist on whether severe infantile cases are also resurging and the extent to which severe pertussis incidence in infants varies by sex and race. We therefore assessed recent US trends in overall and sex- and race-stratified incidence of infant pertussis-related hospitalizations. Data on pertussis-related hospitalizations (ICD-9-CM discharge codes 033.0, 033.8, 033.9, 484.3) from the 2000-2011 Nationwide Inpatient Sample (NIS) were retrospectively analyzed. Annual pertussis-related hospitalizations per 10,000 infants aged <12 months was estimated using NIS sampling weights and year-specific population denominators from US census data. Incidence of pertussis-related hospitalization was ~6/10,000 infants between 2000 and 2003 before increasing sharply in 2004 (9.0/10,000) and 2005 (13.8/10,000). Thereafter, incidence fell substantially (6.2, 4.1, and 4.2/10,000 in 2006, 2007, and 2008, respectively) before increasing again in 2009 and 2010 (5.9 and 7.8/10,000, respectively). Incidence declined again in 2011 (3.2/10,000). Incidence was similar between males and females, but substantial differences were observed by race. Incidence was highest in Hispanic infants, starting at 8.6/10,000 in 2000, peaking at 24.9/10,000 in 2005, and then falling to 4.3/10,000 in 2008 before another sharp increase to 14.7/10,000 in 2010. Incidence was lowest for white and Asian infants, reaching a 2005 peak of only 5.4 and 5.3/10,000, respectively. Infant pertussis hospitalizations peaked in 2005 before a sharp decline thereafter, possibly due to increased herd immunity conferred by the 2006 launch of universal adolescent Tdap vaccination. Incidence resurged again through 2010 before another decline in 2011, demonstrating for severe cases the documented cyclic pattern of peaks and nadirs for overall pertussis incidence. This analysis also highlights the need for increased focus on minorities in pertussis vaccination programs.