JAMA Network Open.Ĭorresponding Author: Amanda K. Open Access: This is an open access article distributed under the terms of the CC-BY License. 6 However, more research is needed to understand protection against emerging variants based on natural vs vaccine-derived immunity. Therefore, some countries may consider prioritizing vaccination for those without measurable antibodies, a strategy used in prior vaccination campaigns when shortages exist. Additional studies are also needed to determine whether antibody levels represent lasting immunity to the evolving SARS-CoV-2.Īs vaccine supply remains limited globally, those with naturally derived antibodies may contribute to herd immunity. This study was limited by its use of a convenience sample nested within a longitudinal cohort of hospital workers, which means results may not be generalizable. Our data demonstrate durability of IgG titers well beyond this period and extend recently published intervals of 6 to 8 months. The Centers for Disease Control and Prevention acknowledges that prior SARS-CoV-2 infection reduces the risk of reinfection for a minimum 90-day period. Our results demonstrated the durability of spike antibodies to SARS-CoV-2 up to 10 months after natural infection. In participants with multiple tests postinfection, the within-participant rate of decay was 7% (95% CI, 3%-11%) per month. The estimated rate of IgG decay was 7% per month (95% CI, 3%-10%). IgG antibodies were positive in 72% (8 of 11) of those tested more than 250 days postinfection. Fifty-two of 59 (88%), 30 of 40 (75%), and 25 of 33 (76%) HWs who tested less than 100, 100 to 200, and more than 200 days post-PCR were IgG positive, respectively. The median spike IgG antibody ratios as a function of days from positive PCR test are shown in the Figure. Of the 94 HWs, 90 (96%) were non-Hispanic/Latino and 70 (74%) were White the median (IQR) age of HWs tested after PCR-positive results was 37.5 (31.1-46.7) years ( Table). The threshold for statistical significance was α < .05 in 2-sided tests.Īmong the cohort of 3015 HWs (2359 women median age, 38.4 years), 170 (5.6%) HWs had positive PCR results for SARS-CoV-2, of which only 94 (3.1%) were tested for spike antibodies after infection but before vaccination (57 HWs received 1 antibody test after PCR positive, 36 received 2 tests, and 1 received 3 tests). Analysis was conducted using R version 4.0.2 (R Project for Statistical Computing). A sensitivity analysis, including only HWs with multiple serum samples, estimated the within-participant relative change in IgG by separating the cross-sectional and longitudinal effect of time. A linear mixed model with random intercept for each HW quantified the relative change in serum IgG ratio per day from a positive PCR test. Median serum IgG ratios as a function of time (ie, days from positive PCR test) were visualized using a natural cubic spline (with 2 df) with 95% bootstrap CIs to account for multiple serum samples within HWs. We applied an internally derived IgG cutoff ratio (>1.23) for greater sensitivity and specificity with an upper threshold of 11 based on assay saturation. Serum specimens were tested using an enzyme-linked immunosorbent assay (Euroimmun) that targets the S1 subunit of the SARS-CoV-2 spike protein and measures optical density ratios. A convenience sample of HWs who tested positive for SARS-CoV-2 and then had at least 1 positive anti–SARS-CoV-2 IgG measurement prior to vaccination were included in this analysis. SARS-CoV-2 polymerase chain reaction (PCR)–testing and immunization data were collected from electronic health records. Participants provided serum samples and completed surveys (including providing demographic data and exposures) every 3 to 4 months after enrollment. Cohort results followed the Strengthening the Reporting of Observational Studies in Epidemiology ( STROBE) reporting guideline. This study was approved by the Johns Hopkins University institutional review board. Shared Decision Making and Communicationīeginning in June 2020, 3015 hospital workers (HWs) at 5 regional hospitals in the Johns Hopkins Health System consented to participate and were enrolled in a prospective cohort study to determine the seroprevalence of spike antibodies to SARS-CoV-2.Scientific Discovery and the Future of Medicine.Health Care Economics, Insurance, Payment. Clinical Implications of Basic Neuroscience.Challenges in Clinical Electrocardiography.
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