Epidemiology of invasive Streptococcus pneumoniae infections in the United States, 1995-1998: Opportunities for prevention in the conjugate vaccine era

CONTEXT

Pneumococcal polysaccharide vaccine is recommended for elderly persons and adults with certain chronic illnesses. Additionally, a recently licensed pneumococcal 7-valent conjugate vaccine has been recommended for use in young children and could dramatically change the epidemiology of pneumococcal disease.

OBJECTIVES

To assess pneumococcal disease burden in the United States, estimate the potential impact of new vaccines, and identify gaps in vaccine recommendations.

DESIGN AND SETTING

Analysis of data from the Active Bacterial Core Surveillance (ABCs)/Emerging Infections Program Network, an active, population-based system in 9 states.

PATIENTS

A total of 15 860 cases of invasive pneumococcal disease occurring between January 1, 1995, and December 31, 1998.

MAIN OUTCOME MEASURES

Age- and race-specific pneumoccocal disease incidence rates per 100 000 persons, case-fatality rates, and vaccine preventability.

RESULTS

In 1998, overall incidence was 23.2 cases per 100 000, corresponding to an estimated 62 840 cases in the United States. Incidence was highest among children younger than 2 years (166.9) and adults aged 65 years or older (59.7). Incidence among blacks was 2.6 times higher than among whites (95% confidence interval [CI], 2.4-2.8). Overall, 28.6% of case-patients were at least 65 years old and 85.9% of cases in this age group were due to serotypes included in the 23-valent polysaccharide vaccine; 19.3% of case-patients were younger than 2 years and 82.2% of cases in this age group were due to serotypes included in the 7-valent conjugate vaccine. Among patients aged 2 to 64 years, 50.6% had a vaccine indication as defined by the Advisory Committee on Immunization Practices (ACIP). The case-fatality rate among patients aged 18 to 64 years with an ACIP indication was 12.1% compared with 5.4% for those without an indication (relative risk, 2.2; 95% CI, 1.7-2.9).

CONCLUSIONS

Young children, elderly persons, and black persons of all ages are disproportionately affected by invasive pneumococcal disease. Current ACIP recommendations do not address a subset of persons aged 18 to 64 years but do include those at highest risk for death from invasive pneumococcal disease.

Increasing prevalence of multidrug-resistant Streptococcus pneumoniae in the United States

BACKGROUND

The emergence of drug-resistant strains of bacteria has complicated treatment decisions and may lead to treatment failures.

METHODS

We examined data on invasive pneumococcal disease in patients identified from 1995 to 1998 in the Active Bacterial Core Surveillance program of the Centers for Disease Control and Prevention. Pneumococci that had a high level of resistance or had intermediate resistance according to the definitions of the National Committee for Clinical Laboratory Standards were defined as "resistant" for this analysis.

RESULTS

During 1998, 4013 cases of invasive Streptococcus pneumoniae disease were reported (23 cases per 100,000 population); isolates were available for 3475 (87 percent). Overall, 24 percent of isolates from 1998 were resistant to penicillin. The proportion of isolates that were resistant to penicillin was highest in Georgia (33 percent) and Tennessee (35 percent), in children under five years of age (32 percent, vs. 21 percent for persons five or more years of age), and in whites (26 percent, vs. 22 percent for blacks). Penicillin-resistant isolates were more likely than susceptible isolates to have a high level of resistance to other antimicrobial agents. Serotypes included in the 7-valent conjugate and 23-valent pneumococcal polysaccharide vaccines accounted for 78 percent and 88 percent of penicillin-resistant strains, respectively. Between 1995 and 1998 (during which period 12,045 isolates were collected), the proportion of isolates that were resistant to three or more classes of drugs increased from 9 percent to 14 percent; there also were increases in the proportions of isolates that were resistant to penicillin (from 21 percent to 25 percent), cefotaxime (from 10 percent to 15 percent), meropenem (from 10 percent to 16 percent), erythromycin (from 11 percent to 16 percent), and trimethoprim-sulfamethoxazole (from 25 percent to 29 percent). The increases in the frequency of resistance to other antimicrobial agents occurred exclusively among penicillin-resistant isolates.

CONCLUSIONS

Multidrug-resistant pneumococci are common and are increasing. Because a limited number of serotypes account for most infections with drug-resistant strains, the new conjugate vaccines offer protection against most drug-resistant strains of S. pneumoniae.

Mortality from invasive pneumococcal pneumonia in the era of antibiotic resistance, 1995-1997

OBJECTIVES

This study examined epidemiologic factors affecting mortality from pneumococcal pneumonia in 1995 through 1997.

METHODS

Persons residing in a surveillance area who had community-acquired pneumonia requiring hospitalization and Streptococcus pneumoniae isolated from a sterile site were included in the analysis. Factors affecting mortality were evaluated in univariate and multivariate analyses. The number of deaths from pneumococcal pneumonia requiring hospitalization in the United States in 1996 was estimated.

RESULTS

Of 5837 cases, 12% were fatal. Increased mortality was associated with older age, underlying disease. Asian race, and residence in Toronto/Peel, Ontario. When these factors were controlled for, increased mortality was not associated with resistance to penicillin or cefotaxime. However, when deaths during the first 4 hospital days were excluded, mortality was significantly associated with penicillin minimum inhibitory concentrations of 4.0 or higher and cefotaxime minimum inhibitory concentrations of 2.0 or higher. In 1996, about 7000 to 12,500 deaths occurred in the United States from pneumococcal pneumonia requiring hospitalization.

CONCLUSIONS

Older age and underlying disease remain the most important factors influencing death from pneumococcal pneumonia. Mortality was not elevated in most infections with beta-lactam-resistant pneumococci.

Addressing emerging infections. The partnership between public health and primary care physicians

In response to concerns about emerging infections, the Minnesota Department of Health, in conjunction with the Centers for Disease Control and Prevention, developed a model emerging infections program in 1995. The authors' experience with the program has demonstrated the key role clinicians have as partners with public health agencies in identifying and reporting disease cases, educating patients about infectious risks, and preventing emerging infections. This partnership is well illustrated by two examples from Minnesota: a recent outbreak of Neisseria meningitidis infection in a rural area and a laboratory surveillance study of invasive and drug-resistant Streptococcus pneumoniae infections in a metropolitan area.

Building coalitions: a community wide approach for promoting farming health and safety

1. The context of agriculture in the Midwest, given many smaller, family run operations, presents multiple and complex challenges; occupational health intervention strategies used in other industries are not immediately applicable. 2. Public health nurses in Minnesota's Occupational Health Nurses in Agricultural Communities project (OHNAC) are applying the strategies of community wide health promotion through community organizing for farm health and safety promotion. 3. The theoretical basis for community wide health promotion encompasses theory from several disciplines, and a five stage model for community organization in health promotion has been developed and tested. 4. At the root of tis approach to farm safety is the effort to change long held beliefs and community norms, especially the belief that farm injuries and fatalities are a necessary part of agricultural work.