WEDNESDAY, Oct. 14, 2020 (HealthDay News) — Protective antibodies persist for months in patients who survive serious COVID-19 infections, according to a study published Oct. 8 in Science Immunology.

Anita S. Iyer, from Massachusetts General Hospital in Boston, and colleagues measured plasma and/or serum antibody responses to the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2 in 343 North American patients infected with SARS-CoV-2 (93 percent required hospitalization). Measurements were taken for up to 122 days after symptom onset and were compared to those of 1,548 individuals whose blood samples were obtained prior to the pandemic.

The researchers found that the median time to seroconversion was nearly 12 days across all three isotypes tested, and IgA and IgM antibodies against RBD were short-lived with median times to seroreversion of 71 and 49 days, respectively, after symptom onset. Anti-RBD IgG responses decayed slowly through 90 days with only three seropositive individuals seroreverting within this time period. There was a strong correlation between IgG antibodies to SARS-CoV-2 RBD and anti-S neutralizing antibody titers, which demonstrated little to no decrease over 75 days since symptom onset. There was no cross-reactivity of the SARS-CoV-2 RBD-targeted antibodies with other widely circulating coronaviruses (HKU1, 229 E, OC43, NL63).

“Knowing how long antibody responses last is essential before we can use antibody testing to track the spread of COVID-19 and identify ‘hot spots’ of the disease,” one coauthor said in a statement.

Two authors disclosed ties to the biotechnology industry.

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