Lack of Antibodies to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in a Large Cohort of Previously Infected Persons.

Background: Reports suggest that some persons previously infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) lack detectable immunoglobulin G (IgG) antibodies. We aimed to determine the proportion IgG seronegative and predictors for seronegativity among persons previously infected with SARS-CoV-2.

Methods: We analyzed serologic data collected from healthcare workers and first responders in New York City and the Detroit metropolitan area with a history of a positive SARS-CoV-2 reverse-transcription polymerase chain reaction (RT-PCR) test result and who were tested for IgG antibodies to SARS-CoV-2 spike protein at least 2 weeks after symptom onset.

Results: Of 2547 persons with previously confirmed SARS-CoV-2 infection, 160 (6.3%) were seronegative. Of 2112 previously symptomatic persons, the proportion seronegative slightly increased from 14 to 90 days post symptom onset (P = .06). The proportion seronegative ranged from 0% among 79 persons previously hospitalized to 11.0% among 308 persons with asymptomatic infections. In a multivariable model, persons who took immunosuppressive medications were more likely to be seronegative (31.9%; 95% confidence interval [CI], 10.7%-64.7%), while participants of non-Hispanic Black race/ethnicity (vs non-Hispanic White; 2.7%; 95% CI, 1.5%-4.8%), with severe obesity (vs under/normal weight; 3.9%; 95% CI, 1.7%-8.6%), or with more symptoms were less likely to be seronegative.

Conclusions: In our population with previous RT-PCR-confirmed infection, approximately 1 in 16 persons lacked IgG antibodies. Absence of antibodies varied independently by illness severity, race/ethnicity, obesity, and immunosuppressive drug therapy. The proportion seronegative remained relatively stable among persons tested up to 90 days post symptom onset.