2.2. General Criteria for Study Enrollment

Considerations to enroll individuals as CCP donor candidates were as follow. Only individuals who, (i) had a confirmed SARS-CoV-2 infection, either by real-time reverse transcriptase-polymerase chain reaction from a nasopharyngeal swab specimen or serologically detected SARS-CoV-2 IgG Abs in the serum/plasma, (ii) had a complete resolution of symptoms for at least 14 days prior to donation, (iii) were 18 years old or older, (iv) weighted 60 kg or more at the moment of the study, and (v) that successfully passed a medical examination by a physician, were enrolled in the study as CCP donor candidates. All CCP donor candidates who were recruited for the study donated their plasma for analysis within two months after recovery from COVID-19.

For molecular detection of viral particles, SARS-CoV-2 R-GENE^® assay (bioMérieux, Marcy-l’Étoile, France) was used, according to previously described protocol [25]. For serological detection of anti-SARS-CoV-2 IgG Abs, SARS-CoV-2 IgG II Quant assay (Abbott, North Chicago, IL, USA) and COVID-19 ELISA IgG (Vircell S.L, Granada, Spain) assays were used, according to manufacturer instructions [26].