BACKGROUND: Convalescent plasma products are a potential passive immunotherapy for Coronavirus disease 2019 (COVID-19) disease . Various approaches have been utilized to determine the concentration of Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) -neutralizing antibodies in plasma products . The Canadian Blood Services used Plaque Reduction Neutralization Test 50 (PRNT 50) -generated values to qualify convalescent plasma donations supporting clinical trials in Canada . This manuscript describes changes in PRNT 50 titers of repeat male plasma donations collected approximately 1-4 months after onset of COVID-19 signs and symptoms in donors . STUDY
DESIGN AND METHODS: Men were eligible to donate if they: met standard criteria, were <67 years of age, reported a previous SARS-CoV-2-positive nucleic acid test, and recovered and were symptom free for at least 28 days prior to donation . Repeat donation analysis required at least one original and one repeat donation where a PRNT 50 was performed .
RESULTS: From April 29 , 2020 to July 25 , 2020 , 156 donors donated once, with 78 (50 %) of the donated plasma having PRNT 50 titers of ≥1:160 . Thirty-seven (23.7 %) of the donated plasma had a titer of 1:40 or 1:80 (individuals donating this plasma were asked to donate a second time only). A total of 30 donors (19.2 %) had repeat donations . Of the repeat donors , 15 (50 %) had at least an eightfold change from peak to trough PRNT 50 titers within greater than 90 days after onset of COVID-19 symptoms .
CONCLUSIONS: Blood operators cannot infer that SARS-CoV-2 PRNT 50 will remain high in repeat plasma donors 3-4 months after onset of COVID-19 symptoms.
Index: donors, infectious disease testing, plasma derivatives