{"doi":"10.1017/ice.2021.367","title":"Serologic Status and SARS-CoV-2 Infection over 6 Months of Follow Up in Healthcare Workers in Chicago: A Cohort Study","abstract":"OBJECTIVE: To determine the changes in severe acute respiratory coronavirus virus 2 (SARS-CoV-2) serologic status and SARS-CoV-2 infection rates in healthcare workers (HCWs) over 6-months of follow-up. DESIGN: Prospective cohort study. SETTING AND PARTICIPANTS: HCWs in the Chicago area. METHODS: Cohort participants were recruited in May and June 2020 for baseline serology testing (Abbott anti-nucleocapsid IgG) and were then invited for follow-up serology testing 6 months later. Participants completed monthly online surveys that assessed demographics, medical history, coronavirus disease 2019 (COVID-19), and exposures to SARS-CoV-2. The electronic medical record was used to identify SARS-CoV-2 polymerase chain reaction (PCR) positivity during follow-up. Serologic conversion and SARS-CoV-2 infection or possible reinfection rates (cases per 10,000 person days) by antibody status at baseline and follow-up were assessed. RESULTS: In total, 6,510 HCWs were followed for a total of 1,285,395 person days (median follow-up, 216 days). For participants who had baseline and follow-up serology checked, 285 (6.1%) of the 4,681 seronegative participants at baseline seroconverted to positive at follow-up; 138 (48%) of the 263 who were seropositive at baseline were seronegative at follow-up. When analyzed by baseline serostatus alone, 519 (8.4%) of 6,194 baseline seronegative participants had a positive PCR after baseline serology testing (4.25 per 10,000 person days). Of 316 participants who were seropositive at baseline, 8 (2.5%) met criteria for possible SARS-CoV-2 reinfection (ie, PCR positive >90 days after baseline serology) during follow-up, a rate of 1.27 per 10,000 days at risk. The adjusted rate ratio for possible reinfection in baseline seropositive compared to infection in baseline seronegative participants was 0.26 (95% confidence interval, 0.13-0.53). CONCLUSIONS: Seropositivity in HCWs is associated with moderate protection from future SARS-CoV-2 infection.","journal":"Infection Control and Hospital Epidemiology","year":2021,"id":170223,"datarank":0.5050943744979712,"base_score":3.367295829986474,"endowment":3.367295829986474,"self_citation_contribution":0.5050943744979712,"citation_network_contribution":0.0,"self_endowment_contribution":0.5050943744979712,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":28,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.7209,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2021-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":495533,"name":"Lisa R. Hirschhorn","orcid":"0000-0002-4355-7437","position":1,"is_corresponding":false},{"id":246815,"name":"Elizabeth Gray","orcid":"0000-0001-9298-6927","position":2,"is_corresponding":false},{"id":231215,"name":"Amisha Wallia","orcid":"0000-0002-3183-4062","position":3,"is_corresponding":false},{"id":109447,"name":"Mercedes R. Carnethon","orcid":"0000-0001-7035-0848","position":4,"is_corresponding":false},{"id":583663,"name":"Teresa Zembower","orcid":"0000-0002-7050-6336","position":5,"is_corresponding":false},{"id":702361,"name":"Joyce Ho","orcid":"0000-0003-4191-0054","position":6,"is_corresponding":false},{"id":702993,"name":"Benjamin J. DeYoung","orcid":null,"position":7,"is_corresponding":false},{"id":702362,"name":"Alex Zhu","orcid":"0000-0002-0506-8405","position":8,"is_corresponding":false},{"id":25007,"name":"Laura J. Rasmussen‐Torvik","orcid":"0000-0002-0820-7300","position":9,"is_corresponding":false},{"id":104974,"name":"Babafemi Taiwo","orcid":"0000-0003-2661-9103","position":10,"is_corresponding":false},{"id":521927,"name":"Charlesnika T. Evans","orcid":"0000-0002-0696-8288","position":11,"is_corresponding":false},{"id":328234,"name":"John T. Wilkins","orcid":"0000-0002-8781-1329","position":0,"is_corresponding":true}],"reference_count":16,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-07-18T23:46:19.728805Z","pmid":"34369331","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}