Impact of the 2009 influenza pandemic on pneumococcal pneumonia hospitalizations in the United States

J Infect Dis. 2012 Feb 1;205(3):458-65. doi: 10.1093/infdis/jir749. Epub 2011 Dec 7.

Abstract

Background: Infection with influenza virus increases the risk for developing pneumococcal disease. The A/H1N1 influenza pandemic in autumn 2009 provided a unique opportunity to evaluate this relationship.

Methods: Using weekly age-, state-, and cause-specific hospitalizations from the US State Inpatient Databases of the Healthcare Cost and Utilization Project 2003-2009, we quantified the increase in pneumococcal pneumonia hospitalization rates above a seasonal baseline during the pandemic period.

Results: We found a significant increase in pneumococcal hospitalizations from late August to mid-December 2009, which corresponded to the timing of highest pandemic influenza activity. Individuals aged 5-19 years, who have a low baseline level of pneumococcal disease, experienced the largest relative increase in pneumococcal hospitalizations (ratio, 1.6 [95% confidence interval {CI}, 1.4-1.7]), whereas the largest absolute increase was observed among individuals aged 40-64 years. In contrast, there was no excess disease in the elderly. Geographical variation in the timing of excess pneumococcal hospitalizations matched geographical patterns for the fall pandemic influenza wave.

Conclusions: The 2009 influenza pandemic had a significant impact on the rate of pneumococcal pneumonia hospitalizations, with the magnitude of this effect varying between age groups and states, mirroring observed variations in influenza activity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Child
  • Child, Preschool
  • Female
  • Hospitalization / statistics & numerical data*
  • Humans
  • Infant
  • Infant, Newborn
  • Influenza A Virus, H1N1 Subtype / isolation & purification
  • Influenza A Virus, H1N1 Subtype / pathogenicity*
  • Influenza, Human / complications*
  • Influenza, Human / virology
  • Male
  • Middle Aged
  • Pandemics*
  • Pneumonia, Pneumococcal / epidemiology*
  • United States / epidemiology
  • Young Adult