COVID-19 Plasma Donors have Higher Levels of IgG 28 Days after Symptom Onset

IgG in COVID-19 convalescent plasma donors seems to attain higher levels four weeks after symptom onset, thus pointing that this is the optimal time to collect plasma. A study of 49 convalescent plasma donors revealed that plasma levels were lower when the donation occurred less than 28 days from the symptom onset in comparison to levels in patients who donated after four weeks. The results were published in Transfusion.

Other factors associated with increased IgG levels in the recovered patients included having had a fever for three or more days or a body temperature that exceeded 101.3 degrees F.

Among the 49 convalescent plasma donors in the study, 90% had a titer of >1:160 and 78% had a titer of ≥ 1:640.

Going by the selection criterion of donating plasma four weeks following symptom onset, there were 42 convalescent plasma donors, 90% of whom had a titer of 1: 160 and 84% had a titer of ≥ 1:640. There was no correlation between S-RBD-specific IgG antibody and age, gender or donor blood type.

In order to further analyze donor characteristics, investigators enroled patients who had recovered from COVID-19, aged 18 to 55 years, were eligible for blood donation, had two negative COVID-19 nasopharyngeal swab tests on PCR at least 24 hours apart, had been discharged from the hospital for more than two weeks and had no COVID-19 symptoms before donation.

IgG was measured using ELISA assay developed in-house. Investigators also confirmed the antibodies neutralized SARS-CoV-2 in cell culture after five days. [Medscape]

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA