Elsevier

Vaccine

Volume 28, Issue 4, 22 January 2010, Pages 889-892
Vaccine

Short communication
Declining invasive pneumococcal disease mortality in the United States, 1990–2005

https://doi.org/10.1016/j.vaccine.2009.10.121Get rights and content

Abstract

PCV7 use in the U.S. has led to notable decreases in invasive pneumococcal disease (IPD). We examined PCV7 influence on IPD mortality for all age groups using National Multiple-Cause-of-Death data (1990–2005). Age-specific mortality rates were compared before and after PCV7 use. Average decreases in age-adjusted mortality rates for meningitis and septicemia accelerated post-PCV7, the greatest decline observed in septicemia-related deaths. The youngest and oldest age groups experienced large decreases in age-specific mortality rates after the introduction of PCV7. Mortality rate decline across all age groups strengthens evidence of vaccine-induced herd immunity and provides additional information for cost–benefit analyses of PCV7.

Introduction

Streptococcus pneumoniae (pneumococcus), a leading cause of bacterial meningitis in the United States (U.S.) [1], is a cause of significant morbidity and mortality in the U.S. However, expanded immunization, including availability of the pneumococcal conjugate vaccine, has led to declining incidence. During 1998–1999, before the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7), the incidence of invasive pneumococcal disease (IPD) was 96.7 cases/100,000 population in children under 5 years of age and 60.1 cases/100,000 population in persons 65 years of age or older [2]. In 2003, after the introduction of PCV7, the incidence of IPD declined to 23.9/100,000 population in children under 5 years of age (a 75% decrease) and 41.7/100,000 population in persons 65 years or older (a 31% decrease) [2].

In 2000, PCV7 was licensed in the U.S. for use in young children, including those <2 years of age, unlike the polysaccharide vaccine (PPV). The seven serotypes contained in PCV7 (4, 6B, 9V, 14, 18C, 19F, and 23F) are the most common serotypes isolated in the blood or CSF in young children and account for approximately 80% of the infections in this age group in the U.S. [3]. Studies have found the efficacy of PCV7 to be 97.4% in fully vaccinated children [4]. PCV7 has been shown to decrease the incidence of invasive diseases such as pneumococcal meningitis and pneumococcal septicemia [4], [5]. From August 2001 until May 2003 there was a vaccine shortage that led to vaccine coverage levels of only 41% in the U.S. [6], [7], [8]. Despite these low coverage levels, several studies found that the incidence of IPD decreased in the U.S. each year following the introduction of PCV7, especially in vaccine serotypes [2], [9], [10], [11]. In addition, recent studies reported a decrease in pneumococcal-related mortality and case fatality rates in adults [5], [12]. However, most of these reports have not used population-based data and few studies have assessed the trends in pneumococcal-related mortality in all age groups, not just young children or the elderly. We examined national death certificate data to evaluate trends in mortality from IPD in the U.S. in all ages.

Section snippets

Methods

Mortality rates were calculated from death certificates from the entire U.S. population. Deaths were selected from the Multiple-Cause-of-Death (MCOD) data files, 1990–2005. These files, compiled by the National Center for Health Statistics (NCHS), contain both underlying and contributing causes of death as reported on U.S. death certificates. These data also include demographic information, date of death, place of death, and country of origin.

Deaths due to pneumococcal disease were identified

Results

The MCOD data files contained over 37 million deaths reported from 1990 to 2005, including 1999 and 2000. Of these, 13,772 had an IPD reported as an underlying or contributing cause of death, 3692 had pneumococcal meningitis reported as an underlying or contributing cause of death, and 10,662 had pneumococcal septicemia reported as an underlying or contributing cause of death (data not shown). Overall IPD mortality and both pneumococcal meningitis and pneumococcal septicemia mortality rates

Discussion

The findings of this study demonstrate that although IPD continues to be an important cause of potentially preventable mortality in the U.S., a substantial reduction in mortality has followed utilization of PCV7. Decreases in mortality across most age groups suggest a possible benefit of the indirect effect of vaccine through increased vaccine-induced herd immunity.

During the study period the greatest decrease in pneumococcal meningitis mortality was observed in children <2 years (71%), the

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