The antibody levels to SAR-CoV-2, the virus that causes COVID-19, substantially drop in the weeks following infection, according to a study led by Vanderbilt University Medical Center and the Centers for Disease Control and Prevention (CDC).
In an April study of 19 health care workers at VUMC with detectable antibodies to SARS-CoV-2, 58% had antibody levels drop below the threshold of positivity 60 days later.
The story appears in today’s Journal of the American Medical Association (JAMA).
The presence of antibodies indicates a likely prior infection. The investigators believe the antibody changes are likely to be similar in other groups (non health care workers).
“The fact that circulating anti-SARS-CoV-2 antibodies substantially drop in the weeks and months following infection has several important implications,” said Wesley Self, MD, MPH, associate professor of Emergency Medicine at VUMC and the study’s senior author.
“First, because antibody levels drop relatively quickly after recovery from the infection, testing for detectable antibodies in groups of healthy people in the population may underestimate the proportion of the population who had COVID-19 previously, because people who previously had COVID-19 may not have antibodies detectable any longer at the time of test,” he said.
“Second, this helps demonstrate the window in which it is best for patients who have recovered from COVID-19 to donate plasma for use as COVID convalescent plasma therapy in other patients — within the first few months of recovering from COVID-19 — because the antibody levels are highest in that time window and then appear to drop.”
Convalescent plasma therapy uses blood from people who have recovered from an illness to help others recover. The U.S. Food and Drug Administration issued an emergency use authorization for convalescent plasma therapy for people with COVID-19, and there are ongoing clinical trials evaluating its effectiveness as a treatment for the disease.
Self said that another important finding is that, compared with asymptomatic health care workers, those with symptoms had higher antibody levels and were less likely to become seronegative at 60 days. This is consistent with a recent report from China that was published in the journal Nature Medicine.
The team is continuing to study antibody and other immune responses to SARS-CoV-2 infection.
The study, funded by the Centers for Disease Control and Prevention (CDC) is part of ongoing work conducted by the IVY Network, a 14-site research network led by VUMC that studies influenza and COVID-19. The IVY Network has conducted a series of studies on COVID-19, including infections among health care workers throughout the United States.
The Vanderbilt health care workers enrolled in the study were from the Emergency Department, the COVID stepdown unit in Medical Center East and the Medical Intensive Care Unit.
Manish Patel, MD, of the CDC, is the current study’s first author.
