Trends in U.S. Hospitalizations and Inpatient Deaths from Pneumonia and Influenza, 1996-2011 Open Access

Chang, D.H. (2015)

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Background To reduce excessive morbidity and mortality of pneumonia and influenza (P&I), the Advisory Committee on Immunization Practices (ACIP) has recommended the use of 23-valent pneumococcal polysaccharide vaccine (PPSV23), 7-valent pneumococcal conjugate vaccine (PCV7), and 13-valent pneumococcal conjugate vaccine (PCV13) over the past two decades, as well as incrementally expanded the target group for annual influenza vaccination of healthy persons, to ultimately include all persons >= 6 months of age without contraindications as of the 2010-11 influenza season. There has not been a published study of trends in P&I hospitalizations in the U.S since 2002.

Methods Using the Nationwide Inpatient Sample, we constructed and analyzed annual and monthly rates of P&I hospitalization and inpatient death from 1996 to 2011, adjusted for sex and age. P&I hospitalizations were defined as a principal diagnosis of P&I, or a principal diagnosis of sepsis or respiratory failure, accompanied by a secondary diagnosis of P&I. Rate differences, and reductions in P&I hospitalizations and inpatient deaths in absolute and relative terms were calculated to summarize the changes during the study period.

Results Overall rates of P&I hospitalizations and inpatient deaths declined by 26 per 100,000 (5%) and by 5.7 per 100,000 (13%), respectively. This translates to 81,000 fewer P&I hospitalizations and 17,800 fewer P&I inpatient deaths in 2011 compared to 1996. The rates of P&I hospitalization dropped the most among children aged <2 (50% decrease; absolute decrease of 638 per 100,000), followed by seniors aged 65+ (7% decrease; absolute decrease of 167 per 100,000). The rates of P&I inpatient death declined the most among seniors aged 65+ (19% decrease; absolute decrease of 52.0 per 100,000).

Conclusions In this nationally representative study, P&I hospitalizations and inpatient deaths decreased in the U.S. between 1996 and 2011. While it is difficult to attribute these changes directly to specific vaccines in this era, overall epidemiologic changes in P&I hospitalizations and inpatient deaths are likely to be due to the introduction of PCV7, and the expansion of the target group for annual influenza vaccination of healthy persons.

Table of Contents

Chapter I: Background. 1

Pneumonia and Influenza. 1

Pneumococcal vaccines. 3

Influenza vaccines. 4

Study rationale, and objectives. 5

Chapter II: Manuscript. 7

Introduction. 7

Methods. 8

Study population. 8

Definition of hospitalizations for pneumonia and influenza. 8

Data analysis methods. 9

Disclosures. 9

Results. 10

Discussion. 12

Conclusion. 15

Chapter III: Summary, Public Health Implications, Possible Future Directions. 16

References. 19

Appendices. 29

Figures. 29

Figure Legends. 29

Figure 1. 33

Figure 2. 34

Figure 3. 35

Figure S1. 36

Figure S2. 37

Tables. 38

Table 1. Sex and Age-adjusted Rate Differences, Percent Reduction, and Absolute Reduction in Hospitalizations and Inpatient Deaths from Pneumonia and Influenza in the U.S., Year 1996 vs 2011. 38

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