Characteristics and serological patterns of COVID-19 convalescent plasma donors: optimal donors and timing of donation.

This study indicates that the S-RBD-specific IgG antibody reaches higher levels after 4 weeks from the onset of COVID-19 symptoms. We recommend the following selection criteria for optimal donation of COVID-19 convalescent plasma: 28 days after the onset of symptoms and with a disease presentation of fever lasting longer than 3 days or a body temperature exceeding 38.5°C. Selection based on these criteria can ensure a high likelihood of achieving sufficiently high S-RBD-specific IgG titers.