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Immune Response Strong After One Dose in COVID-19-Seropositive Vaccinees

FRIDAY, March 12, 2021 -- Individuals with preexisting immunity receiving an mRNA vaccine for COVID-19 have higher antibody titers after one dose than those without preexisting immunity, according to a letter to the editor published online March 10 in the New England Journal of Medicine.

Florian Krammer, Ph.D., from the Icahn School of Medicine at Mount Sinai in New York City, and colleagues examined antibody responses in 110 participants with or without documented preexisting severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2): 67 were seronegative and 43 were seropositive.

The researchers found that most seronegative participants had variable and relatively low SARS-CoV-2 immunoglobulin G responses within nine to 12 days after vaccination (median area under the curve [AUC]: 1; 1; 1; 439; 1,016; 1,037; 1,293; and 3,316 before vaccination; at zero to four days; five to nine days; nine to 12 days; 13 to 16 days; 17 to 20 days; 21 to 27 days; and after the second dose, respectively). Seropositive participants rapidly developed uniform, high antibody titers within days after vaccination (median AUC: 90; 133; 14,208; 20,783; 25,927; 11,755; 19,534; and 22,509 before vaccination; at zero to four days; five to nine days; nine to 12 days; 13 to 16 days; 17 to 20 days; 21 to 27 days; and after the second dose, respectively). Vaccinees with preexisting immunity had antibody titers that were 10 to 45 times as high as those of vaccinees without preexisting immunity at the same time points after the first vaccine dose.

"These findings suggest that a single dose of vaccine elicits a very rapid immune response in individuals who have tested positive for COVID-19," Krammer said in a statement.

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