Production of High-Quality Antibodies Continues 5-7 Months After SARS-CoV-2 Infection, Finds New Study

A study of the production of antibodies from a sample of nearly 6,000 people who recovered from COVID-19 has revealed that immunity persists for at least several months after being infected with SARS-CoV-2.

One of the most significant questions about the novel coronavirus is whether people who are infected are immune from reinfection and, if so, for how long. When a virus first infects cells, the immune system deploys short-lived plasma cells that produce antibodies to immediately fight the virus. Those antibodies appear in blood tests within 14 days of infection. The second stage of the immune response is the creation of long-lived plasma cells, which produce high-quality antibodies that provide lasting immunity.

Researchers from the University of Arizona Health Sciences (Tucson, AZ, USA) tracked antibody levels over several months in people who tested positive for SARS-CoV-2 antibodies. The team also developed a blood test to check for SARS-CoV-2 antibodies by employing two different parts of the SARS-CoV-2 virus - S1 and S2. Most tests look for antibodies at S1, which includes the receptor-binding domain wherein the spike protein binds to a protein receptor to infect cells. The UArizona Health Sciences test also analyzes the S2 region of the spike protein. Antibodies must be present in both locations for the test to be determined positive.

For the study, 5,882 volunteers underwent antibody testing using the UArizona Health Sciences test. The researchers found SARS-CoV-2 antibodies are present in blood tests at viable levels for at least five to seven months, although they believe immunity lasts much longer. Earlier studies had extrapolated antibody production from initial infections and suggested antibody levels drop quickly after infection, providing only short-term immunity. The UArizona Health Sciences researchers believe that those conclusions focused on short-lived plasma cells and failed to take into account long-lived plasma cells and the high-affinity antibodies they produce.

“We clearly see high-quality antibodies still being produced five to seven months after SARS-CoV-2 infection,” said Deepta Bhattacharya, PhD, associate professor, UArizona College of Medicine – Tucson, Department of Immunobiology. “Many concerns have been expressed about immunity against COVID-19 not lasting. We used this study to investigate that question and found immunity is stable for at least five months.”

“Whether antibodies provide lasting protection against SARS-CoV-2 has been one of the most difficult questions to answer,” said UArizona Health Sciences Senior Vice President Michael D. Dake, MD, who is a co-author on the paper. “This research not only has given us the ability to accurately test for antibodies against COVID-19, but also has armed us with the knowledge that lasting immunity is a reality.”

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