23-valent pneumococcal polysaccharide vaccine (PPV23) for the prevention of invasive pneumococcal diseases (IPDs) in the elderly: is it really effective?

Introduction. Incidence of invasive pneumococcal diseases\r\n(IPDs) in Italy is constantly increasing and that is particularly true\r\namong the elderly. 23-valent polysaccharide pneumococcal vaccine\r\n(PPV23) is recommended to this age group and offered in all\r\nItalian regions. However, efficacy of PPV23 on preventing IPDs is\r\ndebated. We therefore performed a review of the most recent available\r\nmeta-analyses in order to assess the efficacy of PPVs.\r\nMethods. The literature search was conducted using PubMed and\r\nScopus search engines. We used the following keywords: “pneumococcal”,\r\n“polysaccharide”, “vaccine”, “efficacy”, “elderly”,\r\n“meta analysis”. Only meta-analyses published in the last 7 years\r\nwere selected. We examined the results of the selected meta-analyses\r\nand assessed their quality according to the PRISMA recommendations.\r\nResults. The search returned 16 results in PubMed and 12 in\r\nScopus: among them we selected 3 meta-analyses. According to\r\nour quality assessment, all meta-analyses showed generally positive\r\nresults and almost all items of the PRISMA checklist were\r\nrespected. However, the research protocol and the registration\r\nnumber were absent in all the 3 revisions and the flow-chart was\r\nnot shown in Moberley’s and Melegaro’s works.\r\nIn the study by Huss et al. the relative risk of developing IPDs\r\namong vaccinated subjects was 0.90 (95%CI: 0.46-1.77, I² 4.9%),\r\nindicating a very slight benefit after vaccination. This contrasts with\r\nthe results of the Cochrane Review by Moberley et al., in which the\r\nPPVs showed a protective efficacy in reducing the risk of IPDs of\r\n74% (OR 0.26, 95%CI: 0.15-0.46) with no statistical heterogeneity\r\n(I² 0%). Melegaro et al. found a reduction not statistically significant\r\nof the incidence of IPD of 65% (OR 0.35; 95%CI 0.08-1.49)\r\namong healthy elderly, while the global estimate of vaccine efficacy\r\namong high risk elderly was minimal (OR 0.80; 95%CI 0.22-2.88).\r\nConclusions. Most of the studies suggest that the PPVs confer\r\nlow protection against IPDs. Anyhow, their methodological heterogeneity\r\ndoes not allow definitive conclusions.\r\nWhile waiting to see the results of new trials about the efficacy\r\nof PPVs, in particular of PPV23, and the extension of the use of\r\nconjugate vaccine among the population over 65, stakeholders\r\nshould be aware of the results of the meta-analyses discussed in\r\nthis paper during the implementation of the vaccination programs\r\nfor the elderly in Public Health