Active pharmacovigilance of the seasonal trivalent influenza vaccine produced by Instituto Butantan: A prospective cohort study of five target groups.

• Main Authors: Tazio Vanni, Beatriz da Costa Thomé, Mayra Martho Moura de Oliveira, Vera Lúcia Gattás, Maria da Graça Salomão, Marcelo Eiji Koike, Maria Beatriz Bastos Lucchesi, Patrícia Emília Braga, Roberta de Oliveira Piorelli, Juliana Yukari Koidara Viscondi, Gabriella Mondini, Anderson da Silva, Heloísa Maximo Espínola, Joane do Prado Santos, Samanta Hosokawa Dias de Nóvoa Rocha, Lily Yin Weckx, Olga Menang, Muriel Soquet, Alexander Roberto Precioso
• Format: Article
• Language: English
• Published: Public Library of Science (PLoS) 2021-01-01
• Series: PLoS ONE
• Online Access: https://doi.org/10.1371/journal.pone.0246540

<h4>Introduction</h4>Active pharmacovigilance studies are pivotal to better characterize vaccine safety.<h4>Methods</h4>These are multicenter prospective cohort studies to evaluate the safety of the 2017 and 2018 seasonal trivalent influenza vaccines (TIVs) manufactured by Instituto Butantan, by means of active pharmacovigilance practices. Elderly, children, healthcare workers, pregnant women, and women in the puerperium period were invited to participate in the study during the 2017 and 2018 Brazilian national seasonal influenza vaccination campaigns. Following immunization, participants were observed for 30 minutes and they received a participant card to register adverse events information. All safety information registered were checked at a clinical site visit 14 days after immunization and by a telephone contact 42 days after immunization for unsolicited Adverse Events (AE) and Guillain-Barré Syndrome (GBS).<h4>Results</h4>A total of 942 volunteers participated in the two studies: 305 elderly, 109 children, 108 pregnant women, 32 women in the postpartum period, and 388 health workers. Overall, the median number of AR per participant ranged from 1 to 4. The lowest median number of AR per participant was observed among healthcare workers (1 AR per participant) and the highest among pregnant women (4 AR per participant). Overall, local pain (46.6%) was the most frequent solicited local AR. The most frequent systemic ARs were: headache (22.5%) followed by fatigue (16.0%), and malaise (11.0%). The majority of solicited ARs (96%) were mild, Grades 1 or 2), only 3% were Grade 3, and 1% was Grade 4. No serious AEs, including Guillain-Barré Syndrome, were reported up to 42 days postvaccination.<h4>Conclusion</h4>The results from the two studies confirmed that the 2017 and 2018 seasonal trivalent influenza vaccines produced by Instituto Butantan were safe and that active pharmacovigilance studies should be considered, when it is feasible, as an important initiative to monitor vaccine safety in the post-marketing period.