Introduction: To combat the COVID-19 pandemic, a mass vaccination campaign was initiated in Italy on December 27, 2020. The vaccine available to immunize Italian healthcare workers (HCWs) was the BNT162b2 mRNA COVID-19 vaccine (Comirnaty). Many studies have shown the high effectiveness of this vaccine in preventing infection and symptomatic disease in the fully immunized.Methods: This study evaluated the effectiveness of the vaccine against documented SARS-CoV-2 infection and symptomatic diseases in the medium- to long-term. HCWs at Bari Policlinico University-Hospital (Italy) who completed the vaccination schedule were matched with HCWs who had refused vaccination;the two groups were followed-up for 5 months (January–May 2021).Findings: Vaccine effectiveness (VE) against infection was 97·7% (95·4–99·0%) at 14–34 days after the first dose, and 94·8% (87·0–97·8%), 83·0% (65·0–92·0%), and 81·0% (42·0-94·0%) at 14–41, 42–69, and >69 days, respectively, after the second dose. The estimated VE for documented symptomatic disease was 99·2% (96·4–99·8%) at 14–34 days after the first dose and 97·2% (90·3–99·2%), 85·0% (63·0–94·2%), and 88·0% (42·0–97·6%) at 14–41, 42–69, and >69 days, respectively, after the second dose.Interpretations: The demonstrated effectiveness and safety of the BNT162b2 mRNA vaccine over the medium- to long-term provides further evidence that it is an essential weapon in ending the COVID-19 pandemic. Efforts to increase vaccination rates should be strengthened, including mandatory vaccination for HCWs and greater incentives to increase vaccine acceptance by the general population.Funding: None to declare. Declaration of Interest: None to declare. Ethical Approval: The research protocol was approved by Apulian Epidemiological Observatory and all human participants gave written informed consent.
BNT162B2 mRNA Covid-19 Vaccine Effectiveness in the Prevention of SARS-CoV-2 Infection and Symptomatic Disease in the Medium - to Long-Term: A Retrospective Cohort Study