Antibody persistence and immunologic memory in children vaccinated with 4 doses of pneumococcal conjugate vaccines: Results from 2 long-term follow-up studies oleh Jacek Wysocki, Jerzy Brzostek, Ryszard Konior, Falko G. Panzer, Nancy A. François, Sudheer M. Ravula, Devayani A. Kolhe, Yue Song, Ilse Dieussaert, Lode Schuerman, Dorota Borys