Antibody Persistence in Adults Two Years after Vaccination with an H1N1 2009 Pandemic Influenza Virus-Like Particle Vaccine. oleh Nuriban Valero-Pacheco, Marisol Pérez-Toledo, Miguel Ángel Villasís-Keever, Adriana Núñez-Valencia, Ilka Boscó-Gárate, Bernardo Lozano-Dubernard, Horacio Lara-Puente, Clara Espitia, Celia Alpuche-Aranda, Laura C Bonifaz, Lourdes Arriaga-Pizano, Rodolfo Pastelin-Palacios, Armando Isibasi, Constantino López-Macías, Constantino López-Macías