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FRIDAY, Oct. 2, 2020 (HealthDay News) — Antibodies decrease with time after COVID-19 symptom onset, according to a research letter published online Oct. 1 in Blood.

Josée Perreault, Ph.D., from Héma-Québec in Montréal, and colleagues analyzed severe acute respiratory syndrome coronavirus 2 spike protein receptor binding domain (RBD) antibody titers from potential COVID-19 convalescent plasma (CCP) donors recruited at least 14 days following COVID-19 symptom resolution.

The researchers found that 6.9 percent of the 282 CCP donors tested seronegative at the time of donation. When considering only donors who had waited for more than 11 to 12 weeks after symptom onset before donating, this proportion increased to about 15 percent. A longitudinal analysis was performed of the anti-RBD antibody response in 11 male and four female CCP donors who donated at least four times during a time interval ranging from 33 to 77 days to 66 to 114 days after symptom onset for the first and last donations, respectively. There was considerable variation between donors in the level of anti-RBD antibodies at the first donation. For all donors, there was a decrease in anti-RBD antibody levels from the first to the last donation. An increase in anti-RBD antibodies was observed in some donors after the first donation, but this was always followed by a decline at later time points.

“The antibodies disappear rapidly, so people recovering from COVID-19 who want to donate blood plasma should not wait too long once they become eligible to donate,” a coauthor said in a statement.

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