Reduction in COVID-19 prevalence in health care workers in a university hospital in southern Brazil after the start of vaccination.

Toniassoa, Sheila de Castro Cardoso; Fernandesa, Fernando Schmidt; Jovelevithsb, Dvora; Filhoc, Fábio Fernandes Dantas; Takahasid, Anderson Yudi; Baldina, Camila Pereira; Pereiraa, Robson Martins; da Silvae, Luciana Pereira; Bruma, Maria Carlota Borba

Introduction: The quick spread of SARS-CoV-2 led to the development of vaccines that are capable of reducing infection and the number of more severe COVID-19 cases. Aim: To assess COVID-19 prevalence among health care workers (HCWs) after vaccination against SARS-CoV-2. Methods: Cross-sectional study on the prevalence of COVID-19 diagnosis among 7.523 HCWs vaccinated against SARS-CoV-2 with Coronavac and ChAdOx1 nCoV-19 in a university hospital, in southern Brazil, between January 18, 2021 and March 18, 2021.The variables evaluated were: sex, age, work area, role, source of infection, previous diagnosis of COVID-19, date of vaccine administration, type of vaccine, and need for hospitalization. The statistical analysis used Poisson regression and Fisher's Exact Test with the SPSS software version 25 and level of significance set at 5%. Results: 813 vaccinated HCWs showed symptoms suggestive of COVID-19, and 35.4% (288) who underwent RT-PCR for SARS-CoV-2 had a detectable result. There was a reduction of 62% in new cases of COVID-19 among HCWs in the institution after seven weeks of the start of the vaccine rollout. Conclusion: Our data suggest that the vaccines used by the institution reduced the number of COVID-19 cases among health care workers, showing the effectiveness of the vaccines.