ABSTRACT
Background/Introduction: COVID-19 has had a significant impact in the last year. Research and implementation of new vaccines against SARS-Cov-2 have given hope of preventing its spread. They have not been tested in the entire population, hence the importance of events presumably attributable to vaccination and immunization (ESAVI's), the results will contribute to the biosafety of the vaccine, improve-ment in the effectiveness of pharmacovigilance of ESAVI's, implementation of measures to combat it. The institutional pharmacovigilance center was fundamental to carry out this study. Objective/Aim: Evaluation of events supposedly attributable to vaccination and immunization by Pfizer vaccine applied in front-line personnel of the National Institute of Cardiology (INC). Methods: Retrospective observational passive pharmacovigilance study of a cohort of first-line health personnel, all of whom worked in the care of patients with COVID-19 in a tertiary level hospital. The data obtained were captured in a database submitted for validation to the pharmacovigilance department and were analyzed. Results: The present study was conducted during the period December 2020 to March 2021, initial doses of Pfizer vaccine were administered to 1950 workers, reporting 59 events;1570 second doses, of which 63 ESAVI's were reported. Of the 127 reports obtained, 5 were discarded due to follow-up problems. The most frequent findings in relation to the total number of doses administered were headache (2.4%), pain/sensitivity at the site of application, asthenia and myalgia with 1.8% respectively, arthralgias (1.6%), fever and adynamia (1.4%). Conclusion: The Pfizer vaccine presented a very low incidence of ESAVI's in the first line personnel of the INC Ignacio Chavez. Symptoms appeared from 30 min to 4 h after application, 75% of the population that presented reaction in the first application, repeated in the subsequent application and it was observed that the persistence of symptoms was longer lasting. The most affected age group was 30-40 years old. Therefore, it is concluded that the analysis of ESAVI's in all vaccines is of great importance to evaluate the safety of each one of them.