SARS-CoV-2 Neutralizing Antibodies Fade Quickly in Recovering COVID-19 Patients After Symptoms Subside

SARS-CoV-2 antibody levels in the blood of COVID-19 patients decline rapidly during the weeks after their bodies have cleared the virus and symptoms have subsided, according to a new study.

Researchers at the University of Montreal (Montreal, QC, Canada) are attempting to understand how the levels of antibodies change over time in order to optimize the use of blood plasma from recovering patients for treating those with severe COVID symptoms. Their research is also critical for understanding the efficacy of COVID-19 vaccines and finding out whether previously infected people face a risk of re-infection. Previous studies have revealed that antibodies against the SARS-CoV-2 spike protein peak two or three weeks following the onset of symptoms. In an earlier study of more than 100 patients by researchers at the University of Montreal, it was found that plasma’s ability to neutralize the SARS-CoV-2 virus declined significantly between three and six weeks after the onset of symptoms.


In the new longitudinal study, the team analyzed blood samples collected at one-month intervals from 31 individuals who were recovering from COVID-19. The researchers measured the levels of immunoglobulins that act against the coronavirus S protein and tested the ability of the antibodies to neutralize SARS-CoV-2. They found that the levels of Immunoglobulins G, A, and M that target the binding site declined between six and 10 weeks after the onset of symptoms and the ability of the antibodies to neutralize the virus also reduced over the same period.

Small studies have found that convalescent plasma can reduce the severity of illness and reduce hospitalization in COVID-19 patients, but it is yet to demonstrate benefits in randomized trials. Recovering patients cannot donate blood until at least 14 days after symptoms have subsided in order to allow their body to clear the viral particles, although the researchers have concluded that convalescent plasma must be collected during a specific window of time after recovery for deriving any clear benefits.

“We don’t want to transfuse the virus, just transfuse the antibodies,” said Andrés Finzi, Ph.D., at the University of Montreal. “But at the same time, our work shows that the capacity of the plasma to neutralize viral particles is going down during those first weeks.”

Related Links:
University of Montreal