title: The effectiveness of the polysaccharide pneumococcal vaccine for the prevention of hospitalizations due to Streptococcus pneumoniae community-acquired pneumonia in the elderly differs between the sexes: results from the Community-Acquired Pneumonia Organization (CAPO) international cohort study.
abstract: BACKGROUND
  The effectiveness of the 23-valent pneumococcal polysaccharide vaccine (PPV23) to prevent hospitalizations due to Streptococcus pneumoniae community-acquired pneumonia (SpCAP) is controversial. Recent literature suggests that vaccine effectiveness may be influenced by sex. In this study, we define the effectiveness of prior PPV23 vaccination for the prevention of hospitalizations due to SpCAP, and evaluate the impact of sex on this effectiveness.
  
  
  METHODS
  This was a nested case-control study from the CAPO international cohort study database. SpCAP was defined as CAP plus S. pneumoniae identified in blood, bronchoalveolar lavage, sputum, or urinary antigen. Vaccination with PPV23 prior to hospitalization was defined as documented in the medical record. A propensity score-weighted logistic regression model was used to calculate odds ratios. The adjusted vaccine effectiveness (aVE) was calculated as 1-adjusted odds ratio.
  
  
  RESULTS
  From a total of 2688 elderly adult hospitalized patients with CAP, SpCAP was identified in 279 (10%). The overall aVE was 37% (95% CI: 10.1-55.4%, P=0.01). For males, the aVE was 34% (95% CI:-1.0% to 57.3%, P=0.06). For females the aVE was 68% (95% CI: 40.3-83.0%, P=0.001).
  
  
  CONCLUSIONS
  PPV23 protects elderly patients from hospitalization due to SpCAP, but female sex drives the effectiveness. Future analysis of vaccine trials should consider the importance of sex as a stratification factor.
authors.affiliation: University of Louisville School of Medicine, Division of Infectious Diseases, Louisville, KY, United States; University of Louisville Clinical and Translational Research Support Unit, Louisville, KY, United States. Electronic address: tlwiem01@louisville.edu.
authors.forename: Timothy L
authors.initials: TL
authors.lastname: Wiemken
authors.affiliation: University of Louisville School of Medicine, Division of Infectious Diseases, Louisville, KY, United States. Electronic address: ruth.carrico@louisville.edu.
authors.forename: Ruth M
authors.initials: RM
authors.lastname: Carrico
authors.affiliation: Johns Hopkins Bloomberg School of Public Health, Department of Molecular Microbiology and Immunology, Baltimore, MD, United States. Electronic address: saklein@jhsph.edu.
authors.forename: Sabra L
authors.initials: SL
authors.lastname: Klein
authors.affiliation: University of Louisville School of Medicine, Department of Microbiology and Immunology, Louisville, KY, United States. Electronic address: cbjons01@louisville.edu.
authors.forename: Colleen B
authors.initials: CB
authors.lastname: Jonsson
authors.affiliation: University of Louisville School of Medicine, Division of Infectious Diseases, Louisville, KY, United States; University of Louisville Clinical and Translational Research Support Unit, Louisville, KY, United States. Electronic address: p0peyr01@louisville.edu.
authors.forename: Paula
authors.initials: P
authors.lastname: Peyrani
authors.affiliation: University of Louisville School of Medicine, Division of Infectious Diseases, Louisville, KY, United States; University of Louisville Clinical and Translational Research Support Unit, Louisville, KY, United States. Electronic address: rrkell01@louisville.edu.
authors.forename: Robert R
authors.initials: RR
authors.lastname: Kelley
authors.affiliation: Department of Health Science, University of Milan Bicocca, Clinica Pneumologica, AO San Gerardo, Via Pergolesi 33, Monza, Italy. Electronic address: stefano.aliberti@unimib.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Aliberti
authors.affiliation: Dipartimento di Fisiopatologia e dei Trapianti, University of Milan, IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico, Via F. Sforza 35, Milan, Italy. Electronic address: francesco.blasi@unimi.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Blasi
authors.affiliation: Pulmonary Training Program, San Juan City Hospital, Puerto Rico. Electronic address: rfernandezg74@gmail.com.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Fernandez-Gonzalez
authors.affiliation: Department of Infectious Diseases, Hospital Profesor Bernardo Houssay, Vicente López, Buenos Aires, Argentina. Electronic address: glopardo@intramed.net.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Lopardo
authors.affiliation: University of Louisville School of Medicine, Division of Infectious Diseases, Louisville, KY, United States; University of Louisville Clinical and Translational Research Support Unit, Louisville, KY, United States. Electronic address: jarami01@louisville.edu.
authors.forename: Julio A
authors.initials: JA
authors.lastname: Ramirez
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D015331:Cohort Studies; D017714:Community-Acquired Infections / Q000517:prevention & control; D005260:Female; D006760:Hospitalization; D006801:Humans; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D022242:Pneumococcal Vaccines / Q000627:therapeutic use*; D011018:Pneumonia, Pneumococcal / Q000517:prevention & control*; D012737:Sex Factors
chemical_list: C414006:23-valent pneumococcal capsular polysaccharide vaccine; D022242:Pneumococcal Vaccines
keywords: Immunology; Pneumococcus; Sex differences; Vaccine effectiveness; Vaccinology