PPV23 More Effective in Elderly Females than Males at Preventing S. pneumoniae CAP

SAN FRANCISCO, CA—Elderly females may have a better immune response to the 23-valent pneumococcal polysaccharide vaccine (PPV23) than males for the prevention of S. pneumoniae community-acquired pneumonia, a study concluded at IDWeek 2013.

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Noting there is “significant controversy” regarding the effectiveness of PPV23 for the prevention of S. pneumoniae community-acquired pneumonia in the elderly, Timothy L. Wiemken, PhD, MPH, CIC, University of Louisville, Louisville, KY, and colleagues compared how effective the vaccine was at preventing hospitalization in male and females older than 65 years of age.

The investigators conducted a secondary analysis of the Community-Acquired Pneumonia Organization (CAPO) international cohort study database, which was created in 1999 to facilitate international research in the field of pneumonia.

All adults >65 years of age hospitalized with community-acquired pneumonia from the United States and Europe were included in the analysis; this comprised 3080 patients, 1937 males and 1143 females. Vaccination with the PPV23 before the current hospitalization was defined as reported in the medical record. Community-acquired pneumonia due to S. pneumoniae was considered in a patient with S. pneumoniae identified in blood, urinary antigen, or bronchoalveolar lavage.

For both males and females, 26% of patients were vaccinated with PPV23 prior to hospitalization, Dr. Wiemken noted. S. pneumoniae community-acquired pneumonia was identified in 327 patients, 211 males and 116 females.

The adjusted vaccine effectiveness (defined as 1-adjusted odds ratio) from the multivariable matched analyses was 32% for males (95% CI -5.2–56.6%; P=0.083) and 53% for females (95% CI 5.5–76.7%; P=0.034).

“Trials evaluating the clinical effectiveness of vaccines may need to stratify the results on gender,” Dr. Wiemken concluded.