Effectiveness of the 23-Valent Pneumococcal Polysaccharide Vaccine (PPV23) against Pneumococcal Disease in the Elderly Systematic Review and Meta-Analysis - Falkenhorst, Gerhard; Remschmidt, Cornelius; Harder, Thomas; Hummers-Pradier, Eva; Wichmann, Ole; Bogdan, Christian (Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2017)