title: Pneumococcal colonization in older adults.
abstract: BACKGROUND
  Little is known about pneumococcal carrier states in older adults. The main aim of this study was to evaluate pneumococcal colonization patterns among older adults in two centres in Milan, Italy, before the widespread use of the 13-valent pneumococcal vaccine (PCV13) in this age group, to investigate demographic and clinical features that are associated with pneumococcal colonization and to estimate the potential coverage offered by PCV13.
  
  
  RESULTS
  Among 417 adults ≥65 years old (171, 41.1 %, ≥75 years), 41 (9.8 %) were pneumococcal carriers. Univariate and multivariate analyses revealed that pneumococcal colonization was significantly less common among individuals with underlying co-morbidities than among those without (odds ratio [OR] 0.453, 95 % confidence interval [CI] 0.235-0.875, p = 0.018; adjusted OR 0.503, 95 % CI 0.255-0.992, p = 0.047). Moreover, among these patients, those with cardiac disease had a significantly lower risk of colonization (OR 0.308, 95 % CI 0.119-0.795, p = 0.015; adjusted OR 0.341, 95 % CI 0.13-0.894, p = 0.029). Only one vaccinated subject who received 23-valent polysaccharide pneumococcal vaccine (PPV23) was colonized. Twenty-five (89.3 %) of the subjects who were <75 years old and 9 (75.0 %) of those who were ≥75 years old were colonized by at least one of the serotypes that is included in PCV13, with serotype 19 F being the most common. Respiratory allergies as well as overall co-morbidities were more common in subjects who were positive for only non-PCV13 serotypes compared with negative subjects and those who were carriers of only PCV13 serotypes.
  
  
  CONCLUSIONS
  Although this study included a relatively small number of subjects and has been performed in a limited geographic setting, results showed that pneumococcal colonization in older people is common, and the monitoring of carriers can offer useful information about the circulation of this pathogen among older people and the potential protective effect of pneumococcal vaccines. Because the colonization in most cases involves the strains that are included in PCV13, this vaccine could be useful in the prevention of pneumococcal infections in the overall population of older people. In subjects with respiratory allergies and in those with co-morbidities, the addition of the PPV23 to PCV13 should be recommended. Due to the low vaccination coverage, urgent educational programmes are required to inform older adults and their medical doctors of the risks of pneumococcal infection and the efficacy and safety of the available pneumococcal vaccines.
authors.affiliation: Department of Pathophysiology and Transplantation, Pediatric Highly Intensive Care Unit, Università degli Studi di Milano, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Via Commenda 9, 20122 Milan, Italy.
authors.forename: Susanna
authors.initials: S
authors.lastname: Esposito
authors.affiliation: Department of Medical Sciences and Community Health, Geriatric Unit, Università degli Studi di Milano, Milan, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Mari
authors.affiliation: Department of Biomedical and Clinical Sciences "Luigi Sacco", Università degli Studi di Milano, Milan, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Bergamaschini
authors.affiliation: Department of Clinical Sciences and Community Health, Laboratory of Medical Statistics, Epidemiology and Biometry "G.A. Maccacaro", Università degli Studi di Milano, Milan, Italy.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Orenti
authors.affiliation: Department of Pathophysiology and Transplantation, Pediatric Highly Intensive Care Unit, Università degli Studi di Milano, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Via Commenda 9, 20122 Milan, Italy.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Terranova
authors.affiliation: Department of Pathophysiology and Transplantation, Pediatric Highly Intensive Care Unit, Università degli Studi di Milano, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Via Commenda 9, 20122 Milan, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Ruggiero
authors.affiliation: Department of Pathophysiology and Transplantation, Pediatric Highly Intensive Care Unit, Università degli Studi di Milano, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Via Commenda 9, 20122 Milan, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Ierardi
authors.affiliation: Department of Pathophysiology and Transplantation, Pediatric Highly Intensive Care Unit, Università degli Studi di Milano, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Via Commenda 9, 20122 Milan, Italy.
authors.forename: Monia
authors.initials: M
authors.lastname: Gambino
authors.affiliation: ASP, Pio Albergo Trivulzio, Milan, Italy.
authors.forename: Francesco Della
authors.initials: FD
authors.lastname: Croce
authors.affiliation: Department of Pathophysiology and Transplantation, Pediatric Highly Intensive Care Unit, Università degli Studi di Milano, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Via Commenda 9, 20122 Milan, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Principi
keywords: 13-valent pneumococcal conjugate vaccine; 13-valent pneumococcal vaccine; 23-valent polysaccharide pneumococcal vaccine; Invasive pneumococcal disease; Pneumococcal carriage; Pneumococcal colonization; Pneumococcal vaccination; Prevention; Streptococcus pneumoniae