Abstract
Most SARS-CoV-2 antibody assays cannot distinguish between antibodies that developed after natural infection and those that developed after vaccination. We assessed the accuracy of a nucleocapsid-containing assay in identifying natural infection among vaccinated individuals. A longitudinal cohort composed of health care workers in the Minneapolis/St. Paul area was enrolled. Two rounds of seroprevalence studies separated by 1 month were conducted from November 2020 to January 2021 among 81 participants. Capillary blood from rounds 1 and 2 was tested for IgG antibodies against spike proteins by enzyme-linked immunosorbent assay (spike-only assay). During round 2, IgGs reactive to SARS-CoV-2 nucleocapsid protein (nucleocapsid-containing assay) were assessed. Vaccination status at round 2 was determined by self-report. Area under the curve was computed to determine the discriminatory ability of the nucleocapsid-containing assay for identification of recent infection. Participants had a mean age of 40 years (range, 23 to 66 years); 83% were female. Round 1 seroprevalence was 9.5%. Before round 2 testing, 46% reported vaccination. Among those not recently infected, in comparing vaccinated vs unvaccinated individuals, elevated levels of spike 1 (P<.001) and spike 2 (P=.01) were observed, whereas nucleocapsid levels were not statistically significantly different (P=.90). Among all participants, nucleocapsid response predicted recent infection with an area under the curve of 0.93 (95% CI, 0.88 to 0.99). Among individuals vaccinated more than 10 days before antibody testing, the specificity of the nucleocapsid-containing assay was 92%, whereas the specificity of the spike-only assay was 0%. An IgG assay identifying reactivity to nucleocapsid protein is an accurate predictor of natural infection among a partially vaccinated population, whereas a spike-only assay performed poorly.
【초록키워드】 IgG, Antibody testing, vaccination, Health care, antibody, health care workers, Infection, Spike protein, nucleocapsid protein, Protein, specificity, enzyme-linked immunosorbent assay, Cohort, IgG antibody, SARS-CoV-2 antibody, Accuracy, IgG antibodies, nucleocapsid, female, Health care worker, age, capillary, natural infection, Blood, Antibody assays, Spike proteins, can not, an area, determined by, Vaccination Status, Participants, 95% CI, All participants, enzyme, individual, participant, vaccinated individuals, IgGs, SARS-CoV-2 nucleocapsid, capillary blood, MOST, enzyme-linked immunosorbent, reactive, enrolled, predicted, performed, significantly, reported, composed, elevated, conducted, was determined, determine, individuals, reactivity, Area, statistically, separated, was tested, were assessed, 【제목키워드】 SARS-CoV-2, Seroprevalence, Population, identification, natural,