Improved post-marketing safety surveillance of quadrivalent inactivated influenza vaccine in Mexico using a computerized, SMS-based follow-up system

Quadrivalent influenza vaccines (QIVs) are designed to prevent influenza disease caused by two influenza A viruses (H1N1 and H3N2) and both influenza B lineages. Risk-monitoring of QIVs to identify adverse events (AEs) is necessary as influenza vaccines are reformulated each year. We developed a new active surveillance system (Sistema de Control de Vacunacion; SICOVA) to improve pharmacovigilance in Mexico. Participants (N = 2013) aged 0 - 96 years from nine sites across three influenza seasons (n = 1166 in 2015 - 2016; n = 633 in 2016 - 2017; and n = 214 in 2017 - 2018) agreed to receive text messages 1, 7, 28, and 42 days post-vaccination to know if they had experienced any AEs. The study was completed electronically by 1763 (87.6%) participants; manual follow-up was conducted for 250 participants whose reporting was incomplete. The overall AE rate was 9.09%. At least one AE was reported by 183 participants, of whom 131 (71.58%) did not require a medical visit and 52 (28.42%) needed medical attention, with none requiring hospitalization. Most AEs requiring medical attention occurred in children aged 0 - 5 years (n = 22, 42.31%) and adults aged 31 - 35 years (n = 5, 9.62%). These results are consistent with the established safety profile of Fluzone® Quadrivalent, and show that SICOVA can facilitate surveillance and increase AE reporting in Mexico.