Catch those antibodies before they fall

Falling antibody levels after recovery disease are well documented, including in COVID-19 patients. Wang et al followed neutralizing antibody titers in hospitalized patients starting shortly after symptom onset and demonstrated antibodies peaked at 4 to 5 weeks after disease onset and then declined.2 In the Perreault et al study, the earliest antibody levels were obtained 33 to 53 days after disease onset as their study population was plasma donors, who were $14 days symptom free and never hospitalized. Muecksch et al used neutralizing antibody assays to show similar antibody titer decline in individuals who were weeks after diagnosis, but this declinewas less apparent and highly variable when measuring antibody levels using high-throughput assays.3 Most recently, Gudbjartsson et al followed antibody levels in 48 hospitalized patients for ;100 days after diagnosis and found that these levels change depending on the antibody tests: levels increasing in total immunoglobulin assays, slightly decreasing in immunoglobulin G (IgG) assays, and greatly decreasing in IgM and IgA assays.4 Thus antibody level changes during the few months after diagnosis depend on the assay.