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Risk of SARS-CoV-2 Reinfection by Vaccination Status, Predominant Variant, and Time from Previous Infection: A Cohort Study in Italy

15 Pages Posted: 9 Jun 2022

See all articles by Massimo Vicentini

Massimo Vicentini

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Epidemiology Unit

Francesco Venturelli

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Epidemiology Unit

Pamela Mancuso

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Epidemiology Unit

Eufemia Bisaccia

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Public Health Service

Alessandro Zerbini

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Unit of Clinical Immunology, Allergy and Advanced Biotechnologies

Marco Massari

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Infectious Disease Unit

Andrea Cossarizza

Università degli studi di Modena e Reggio Emilia (UNIMORE) - Department of Medical and Surgical Sciences, and FIL Trial Office

Sara De Biasi

Università degli studi di Modena e Reggio Emilia (UNIMORE) - Department of Medical and Surgical Sciences, and FIL Trial Office

Patrizio Pezzotti

Istituto Superiore di Sanità - Dipartimento Malattie Infettive

Emanuela Bedeschi

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Public Health Service

Paolo Giorgi Rossi

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Epidemiology Unit

The Reggio Emilia COVID-19 Working Group

Independent

More...

Abstract

Background: We evaluated the risk of SARS-CoV-2 reinfection by vaccination status, predominant variant, and time from first infection.

Methods: The cohort includes all residents in Reggio Emilia, on December 31, 2019 and has been followed up until February 28, 2022 for SARS-CoV-2 infection, first or re-infection (i.e. new positivity >90 days after a previous infection). Cox model was used to compare the risk of first vs. second infection, adjusting for age, sex, vaccine doses, and comorbidities.

Findings: The cohort included 538516 residents, 121154 first SARS-CoV-2 infections, and 3739 reinfections (3243 with the Omicron period) were diagnosed. In the pre-Omicron period, three doses of vaccine reduced the risk of infection by 89% (87-90), a previous infection reduced the risk by 90% (88-91), while vaccination and infection reduced the risk by 98% (88-100). In the Omicron period, three doses reduced the risk by 54% (53-55) and infection by 9% (3-14); combined immunity of one dose and infection gave a 56% (53-59) while three doses and infection 78% (75-80). In the pre-Omicron period, protection from reinfection remained above 88% for up to 15 months from the first diagnosis. In the Omicron period, the protection decreased from 71% (65-76) to 21% (10-30) if the first infection occurred <5 months or more than 21 months before.

Interpretation: Natural immunity acquired with previous variants showed low protection to Omicron. The combination of vaccination and natural immunity seems to be more protective than the two taken individually.

Funding Information: This study was partially supported by the Italian Ministry of Health – Ricerca Corrente Annual Programme 2023 and partially funded by the Emilia-Romagna Regional Health authority (DGR 396/2021).

Declaration of Interests: The study authors declare no conflict of interest.

Ethics Approval Statement: The collection of data used for this manuscript (surveillance and contact tracing data) is compulsory according to national laws on infectious diseases. The COVID-19 Italian National Working group on Bioethics has stated that consensus for the collection of this data in the context of the COVID-19 emergency is not mandatory, based on Guideline 12 of the WHO on ethical issues in public health surveillance (Rapporto ISS COVID-19 n. 34/2020 https://www.iss.it/documents/20126/0/Rapporto+ISS+COVID-19+34_2020.pdf) The legal ordinance n. 640 of February 27, 2020 (Ordinanza n. 640, Gazzetta Ufficiale Serie Generale n.50 28-02-2020 https://www.gazzettaufficiale.it/eli/id/2020/02/28/20A01348/sg) explicitly declares Istituto Superiore di Sanità as entitled to collect data for COVID-19 surveillance and contact tracing and that such data can be used and shared, upon anonymization, to advance scientific knowledge on this new disease.

Keywords: SARS-CoV-2, Omicron, Reinfection, Immunity, Epidemiology

Suggested Citation

Vicentini, Massimo and Venturelli, Francesco and Mancuso, Pamela and Bisaccia, Eufemia and Zerbini, Alessandro and Massari, Marco and Cossarizza, Andrea and De Biasi, Sara and Pezzotti, Patrizio and Bedeschi, Emanuela and Rossi, Paolo Giorgi and Group, The Reggio Emilia COVID-19 Working, Risk of SARS-CoV-2 Reinfection by Vaccination Status, Predominant Variant, and Time from Previous Infection: A Cohort Study in Italy. Available at SSRN: https://ssrn.com/abstract=4132329 or http://dx.doi.org/10.2139/ssrn.4132329

Massimo Vicentini

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Epidemiology Unit ( email )

Francesco Venturelli (Contact Author)

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Epidemiology Unit ( email )

Italy
+390522335499 (Phone)

Pamela Mancuso

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Epidemiology Unit ( email )

Eufemia Bisaccia

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Public Health Service ( email )

Alessandro Zerbini

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Unit of Clinical Immunology, Allergy and Advanced Biotechnologies ( email )

Italy

Marco Massari

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Infectious Disease Unit ( email )

Italy

Andrea Cossarizza

Università degli studi di Modena e Reggio Emilia (UNIMORE) - Department of Medical and Surgical Sciences, and FIL Trial Office ( email )

Sara De Biasi

Università degli studi di Modena e Reggio Emilia (UNIMORE) - Department of Medical and Surgical Sciences, and FIL Trial Office ( email )

Patrizio Pezzotti

Istituto Superiore di Sanità - Dipartimento Malattie Infettive ( email )

Italy

Emanuela Bedeschi

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Public Health Service ( email )

Paolo Giorgi Rossi

Azienda Unità Sanitaria Locale (AUSL) - IRCCS di Reggio Emilia - Epidemiology Unit ( email )

Italy

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