Abstract
Streptococcus pneumoniae is currently the leading cause of community-acquired pneumonia (CAP) and lower respiratory tract infections (LRTI) in adults, elderly and high-risk subjects worldwide. The clear benefits of pneumococcal conjugate vaccination in childhood have been accompanied by a decrease of vaccine-serotype invasive diseases among adults in several countries, mainly due to the herd effect mediated by the reduction of vaccine-serotype nasopharyngeal colonization in both age groups, but this reduction in the incidence of pneumonia has not been observed. The “Community Acquired Pneumonia Immunization Trial in Adults” (CAPITA) study provided conclusive evidence about 13-valent pneumococcal conjugate vaccine (PCV13) efficacy in preventing CAP in adults and led Western countries to issue new recommendations for pneumococcal immunization targeting subjects >50 years and high-risk groups, with marked differences with respect to age and/or risk groups immunized, eligibility for reimbursement and national, regional or local implementation. Several Italian regions implemented PCV13 immunization programs in adults and interesting data have been come available in the last years, especially from Liguria, a Northern region with a high and long-lasting pneumococcal vaccine immunological pressure in infants. In this review, currently available evidence from Italy and Liguria regarding pneumococcal carriage, burden of CAP and LRTI, and on-field effectiveness of PCV13 immunization in adults and elderly will be summarized.
Highlights
Streptococcus pneumoniae (Sp) is currently the leading cause of community-acquired pneumonia (CAP) and lower respiratory tract infections (LRTI), two important clinical pictures with a heavy burden in terms of morbidity and mortality especially among adults, elderly and high-risk subjects worldwide, accounting for 25% to 50% of the cases depending on the diagnostic assay, geographic area, and setting [1,2,3,4,5,6,7,8,9,10]
Multiple advantages have derived from the specific technology of pneumococcal conjugate vaccines, compared to first-generation vaccines based on polysaccharides used as antigens [17]
Conjugate vaccinations can induce herd immunity by reducing the nasopharyngeal carriage of Sp through different mechanisms mainly involving the induction of IgA mucosal antibodies, high-titered serum antibodies transudating into naso- and oropharynx and Sp specific anticapsular IgG serum concentrations [18,19,20,21,22,23,24]
Summary
Streptococcus pneumoniae (Sp) is currently the leading cause of community-acquired pneumonia (CAP) and lower respiratory tract infections (LRTI), two important clinical pictures with a heavy burden in terms of morbidity and mortality especially among adults, elderly and high-risk subjects worldwide, accounting for 25% to 50% of the cases depending on the diagnostic assay, geographic area, and setting [1,2,3,4,5,6,7,8,9,10]. The clear benefits of the widespread use of pneumococcal conjugate vaccination in childhood have been accompanied by a decrease in the rates of vaccine-serotype IPD among adults in several countries, mainly due to the herd immunity effect mediated by the reduction of vaccine-serotype nasopharyngeal colonization in both age groups [11,25,26]. Recommendations for pneumococcal immunization across the world, and in particular in Europe, are complex, heterogeneous and frequently updated, differing with regards to age groups and/or risk groups immunized, different types of available vaccine advised for different groups, eligibility for reimbursement and national, regional or local implementation [28] This heterogeneity has a heavy impact on vaccination coverage rates, and marked differences are observed among various countries [30,31,32]. Currently available evidence from Italy and Liguria regarding pneumococcal carriage, clinical burden of pneumococcal-related diseases and on-field effectiveness of PCV13 immunization programs in adults and the elderly will be summarized
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