ABSTRACT
Background: Health care workers (HCW) are at high risk of get infected by SARS CoV-2 and thus they are a priority for vaccination. We hereby aim to investigate whether the risk of severe and moderate systemic symptoms (MSS) after vaccination is higher in HCWs with a history of previous COVID-19. Methods: An online questionnaire was offered to all HCW undergoing anti-SARS CoV-2 mRNA BNT162b2 vaccine. Previous SARS-CoV-2 infection/COVID-19 was recorded. Local and systemic symptoms after each of the two doses were reported. MSS were those either interfering with daily activities or resulting in time off-work. Factors associated to MSS were identified by logistic regression.Findings: 3,078 HCW were included. Previous SARS-CoV-2 infection/COVID-19 occurred in 396 subjects (12·9%). 59·6% suffered from >=1 local or systemic symptom after the first and 73·4% after the second dose. MSS occurred in 6·3% of cases (14·4% with previous vs 5·1% with no COVID-19 pInterpretation: Possible differences in immune reactivity are drivers of MSS among females, younger and previously infected HCWs. Vaccination strategies according to previous COVID-19 along with data on the longevity of immune response need to be further investigated. Funding: NoneDeclaration of Interests: None of the authors have any conflicts of interest to disclose.Ethics Approval Statement: The protocol was approved by the Ethic Committee Area 1, Milan.