• Arianna Pani, Valeria Cento, Chiara Vismara, Daniela Campisi, Federica Di Ruscio, Alessandra Romandini, Michele Senatore, Paolo Andrea Schenardi, Oscar Matteo Gagliardi, Simona Giroldi, Laura Zoppini, Mauro Moreno, Matteo Corradin, Oscar Massimiliano Epis, Nicola Ughi, Irene Cuppari, Roberto Crocchiolo, Marco Merli, Marco Bosio, Silvano Rossini, Massimo Puoti, and Francesco Scaglione.
• Department of Oncology and Hemato-Oncology, Università degli Studi di Milano, Milan, Italy; Chemical-Clinical and Microbiological Analyses, ASST Grande Ospedale Metropolitano Niguarda, Milan, Italy. Electronic address: Arianna.pani@unimi.it.
• Mayo Clin. Proc. 2021 Dec 1; 96 (12): 296629792966-2979.

ObjectiveTo evaluate the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) anti-spike (S) IgG antibody production after vaccination with BNT162b2 and the protection from symptomatic breakthrough infections in health care workers.MethodsThis prospective observational study (RENAISSANCE) had as a primary end point the evaluation of serologic response to BNT162b2 14 days after a second dose. SARS-CoV-2 anti-S IgG antibodies were evaluated with LIAISON SARS-CoV-2 TrimericS IgG assay (DiaSorin S.p.A.), which is able to detect the presence of both binding and neutralizing antibodies for trimeric spike glycoprotein. Participants were recruited from February 1, 2021, to February 22, 2021. Occurrence of vaccine breakthrough infections was assessed by reverse transcription-polymerase chain reaction on symptomatic and contact cases up to June 6, 2021.ResultsOf 2569 staff evaluated, only 4 were nonresponders (0.16%; 95% CI, 0.04% to 0.41%). All 4 nonresponders were severely immunosuppressed and receiving treatment with mycophenolate mofetil or mycophenolic acid. At 14 days after the second dose, 67.5% (1733) of staff had anti-S IgG titers of 2000 BAU/mL or higher; 19.2% (494), between 1500 and 2000 BAU/mL; 9.8% (251), between 1000 and 1500 BAU/mL; and 3.4% (87), 1000 BAU/mL or lower. Women had a higher probability of having higher titers than men (64.5% [1044/1618] vs 58.3% [410/703]; P=.005). This was confirmed after adjustment for age group (odds ratio, 1.275; 95% CI, 1.062 to 1.531; P=.009). Four months after the end of the vaccination program, only 13 participants (0.26%) had experienced a breakthrough SARS-CoV-2 infection, including 1 nonresponder. This was the only participant requiring hospitalization for severe COVID-19.ConclusionThe vaccination campaign among health care workers at the ASST GOM Niguarda has resulted in a marked serologic response and reduction of incident COVID-19 cases. Yet, the lack of protection should not be overlooked in immunocompromised individuals.Copyright © 2021 Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.

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