U.S. hospitalizations for pneumonia after a decade of pneumococcal vaccination

Abstract

Background: The introduction of 7-valent pneumococcal conjugate vaccine (PCV7) into the U.S. childhood immunization schedule in 2000 has substantially reduced the incidence of vaccine-serotype invasive pneumococcal disease in young children and in unvaccinated older children and adults. By 2004, hospitalizations associated with pneumonia from any cause had also declined markedly among young children. Because of concerns about increases in disease caused by nonvaccine serotypes, we wanted to determine whether the reduction in pneumonia-related hospitalizations among young children had been sustained through 2009 and whether such hospitalizations in older age groups had also declined.

Methods: We estimated annual rates of hospitalization for pneumonia from any cause using the Nationwide Inpatient Sample database. The reason for hospitalization was classified as pneumonia if pneumonia was the first listed diagnosis or if it was listed after a first diagnosis of sepsis, meningitis, or empyema. Average annual rates of pneumonia-related hospitalizations from 1997 through 1999 (before the introduction of PCV7) and from 2007 through 2009 (well after its introduction) were used to estimate annual declines in hospitalizations due to pneumonia.

Results: The annual rate of hospitalization for pneumonia among children younger than 2 years of age declined by 551.1 per 100,000 children (95% confidence interval [CI], 445.1 to 657.1), which translates to 47,000 fewer hospitalizations annually than expected on the basis of the rates before PCV7 was introduced. The rate for adults 85 years of age or older declined by 1300.8 per 100,000 (95% CI, 984.0 to 1617.6), which translates to 73,000 fewer hospitalizations annually. For the three age groups of 18 to 39 years, 65 to 74 years, and 75 to 84 years, the annual rate of hospitalization for pneumonia declined by 8.4 per 100,000 (95% CI, 0.6 to 16.2), 85.3 per 100,000 (95% CI, 7.0 to 163.6), and 359.8 per 100,000 (95% CI, 199.6 to 520.0), respectively. Overall, we estimated an age-adjusted annual reduction of 54.8 per 100,000 (95% CI, 41.0 to 68.5), or 168,000 fewer hospitalizations for pneumonia annually.

Conclusions: Declines in hospitalizations for childhood pneumonia were sustained during the decade after the introduction of PCV7. Substantial reductions in hospitalizations for pneumonia among adults were also observed. (Funded by the Centers for Disease Control and Prevention.).

Fig. 1

US age-specific average annual rates of all-cause pneumonia hospitalizations per 100,000, for three periods: 1997–1999 (pre-PCV7), 2001–2006 (early PCV7), and 2007–2009 (late PCV7).

Fig. 2

All-cause pneumonia hospitalizations per 100,000 US children, 2a. Annual rates, 1997–2009; 2b. Average annual rates, 1997–1999, 2001–2006, 2007–2009; the year of 7-valent pneumococcal conjugate vaccine (PCV7) introduction, 2000 is not included. * p<.05 for rate decline from pre-PCV7 years

Fig. 3

All-cause pneumonia hospitalizations per 100,000 US adults, 3a. Annual rates, 1997–2009; 3b. Average annual rates, 1997–1999, 2001–2006, 2007–2009; the year of 7-valent pneumococcal conjugate vaccine (PCV7) introduction, 2000 is not included. * p<.05 for rate decline from pre-PCV7 years; +p<.05 for rate increase from pre-PCV7 years