Instituto de Atención Pediatrica, Apdo 607-1150 La Uruca, San Jose, Costa Rica. Wee Care Pediatrics, 2084N 1700W Suite A, Layton, UT, United States. Guanchipelin, San Rafael, Escazu, Heredia, Costa Rica. Centro de Investigaciones en Pediatría, Guatemala City, Guatemala. Department of Pediatrics, Mackay Memorial Hospital, 92, Sec. 2, Zhongshan N. Rd., Zhongshan District, Taipei City 104, Taiwan. Department of Pediatrics, Chang Gung Children's Hospital, Chang Gung University College of Medicine, No.199, Tunghwa Rd., Taipei, Taiwan. Instituto de Investigación Nutricional, Av. La Molina 1885, Lima 12, Peru. Hospital Materno Infantil José Domingo de Obaldía, Ciudad de David, Chiriqui, Panama. Novartis Vaccines and Diagnostics, Inc., 350 Massachusetts Avenue, Cambridge, MA 02139, United States. Novartis Vaccines and Diagnostics, Inc., 350 Massachusetts Avenue, Cambridge, MA 02139, United States. Electronic address: peter.dull@novartis.com.