Seroprevalence of SARS-CoV-2 in blood donors from the Lodi Red Zone and adjacent Lodi metropolitan and suburban area

Irene Cassaniti, Elena Percivalle, Antonella Sarasini, Giuseppe Cambiè, Edoardo Vecchio Nepita, Roberta Maserati, Alessandro Ferrari, Alfonso Corcione, Raffaella Di Martino, Alice Bonetti, Annapia Di Napoli, Guglielmo Ferrari, Fausto Baldanti

Research output: Contribution to journalArticlepeer-review


Objectives: To define the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in blood donors (referred to the first lockdown area (Lodi Red-Zone) of the Lombardy region and in a contiguous area that was not included in the first lockdown); to define the agreement between a commercial serological assay and a reference microneutralization assay; and to evaluate the persistence of SARS-CoV-2 neutralizing antibodies in a cohort of blood donors. Methods: Blood donors referred to the first lockdown area in Lombardy Region and the neighbouring area were analysed for SARS-CoV-2 IgG-specific antibodies during the period 18 March to 24 June 2020. Serum samples were analysed using both a chemiluminescent immunoassay (LIAISON® SARS-CoV-2 S1/S2 IgG, DiaSorin) for the quantitative characterization of SARS-CoV-2 anti-S1 and anti-S2 IgG antibodies and a neutralizing antibodies (NT-Abs) assay. Results: In the period from 18 March to 24 June, 1922 blood donors were tested for the presence of SARS-CoV-2 IgG showing a prevalence of 378/1922 (19.7%). A subgroup of 1139 blood donors were tested in parallel with a SARS-CoV-2 IgG assay and a microneutralization assay showing a prevalence of 22.2% and 21.6%, respectively. SARS-CoV-2 IgG quantification was correlated with NT-Abs titres. In 78.2% of participants the NT-Abs titre was maintained, but in 15.8% it decreased by one four-fold dilution and in 6.0% it increased by one four-fold dilution. Conclusions: The duration of immunity of SARS-CoV-2 is crucial for the course of the pandemic and for this reason the monitoring of NT Abs is important. Despite a stable NT-Abs titre being observed in the majority of blood donors, our findings need to be validated in a long-term period of follow up.

Original languageEnglish
JournalClinical Microbiology and Infection
Publication statusAccepted/In press - 2021


  • Epidemiology
  • Lodi area
  • Microneutralization assay
  • Serological assay
  • Seroprevalence
  • Severe acute respiratory syndrome coronavirus 2

ASJC Scopus subject areas

  • Microbiology (medical)
  • Infectious Diseases


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