Pierre Van Damme1, Ilse De Coster2, Hilde Revets2, Ananda S Bandyopadhyay3. 1. Centre for the Evaluation of Vaccination, Vaccine and Infectious Disease Institute, University of Antwerp, 2610 Antwerp, Belgium. Electronic address: pierre.vandamme@uantwerpen.be. 2. Centre for the Evaluation of Vaccination, Vaccine and Infectious Disease Institute, University of Antwerp, 2610 Antwerp, Belgium. 3. Bill & Melinda Gates Foundation, Seattle, WA, USA.