Systemic SARS-CoV-2-specific antibody responses to infection and to COVID-19 and BCG vaccination

SARS-CoV-2 infections elicit antibodies against the viral spike (S) and nucleocapsid (N) proteins; COVID-19 vaccines against the S-protein only. The BCG-Corona trial, initiated in March 2020 in SARS-CoV-2-naïve Dutch healthcare workers, captured several epidemic peaks and the introduction of COVID-19 vaccines during the one-year follow-up. We assessed determinants of systemic anti-S1 and anti-N immunoglobulin type G (IgG) responses using trial data. Participants were randomized to BCG or placebo vaccination, reported daily symptoms, SARS-CoV-2 test results, and COVID-19 vaccinations, and donated blood for SARS-CoV-2 serology at two time points. In the 970 participants, anti-S1 geometric mean antibody concentrations (GMCs) were much higher than anti-N GMCs. Anti-S1 GMCs significantly increased with increasing number of immune events (SARS-CoV-2 infection or COVID-19 vaccination): 104.7 international units (IU)/ml, 955.0 IU/ml, and 2290.9 IU/ml for one, two, and three immune events, respectively (p<0.001). In adjusted multivariable linear regression models, anti-S1 and anti-N log10 concentrations were significantly associated with infection severity, and anti-S1 log10 concentration with COVID-19 vaccine type/dose. In univariable models, anti-N log10 concentration was also significantly associated with acute infection duration, and severity and duration of individual symptoms. Antibody concentrations were not associated with Long COVID or long-term loss of smell/taste. ### Competing Interest Statement LV reports consulting fees from MSD in the last 36 months (unrelated to the work in this manuscript, payments to institution). MB reports research grants from Janssen Vaccines, Novartis, CureVac, and Merck, Advisory Board memberships of Spherecydes, Pfizer, MSD, Novartis and AstraZeneca, and DSMB membership of Sanofi, in the last 36 months (unrelated to the work in this manuscript, payments to institution). MN is scientific founder and scientific advisory board member of Trained Therapeutix Discovery (TTxD) and scientific founder of Lemba Therapeutics, has obtained research grants from GSK Biologicals, TTxD, and Ono Pharma, and consultancy fees from TTxD. JW reports payments for meeting attendance from the Dutch Ministry of Health and Sports and the Netherlands Organization for Health Research and Development (ZonMw) in the last 36 months (unrelated to the work in this manuscript, payments to institution). All other authors declare no competing interests. ### Funding Statement The original BCG-Corona trial was not externally funded. The additional work included in this publication is part of the project "BCG vaccination to minimize COVID-19 disease severity and duration" with project number 10430 01 201 0026 of the research programme COVID-19 which is financed by the Netherlands Organization for Health Research and Development (ZonMw). MN was also funded by an ERC Advanced Grant (grant number 833247) and Spinoza grant of the Netherlands Organization for Scientific Research (NWO). LV was also funded by a Hypatia Tenure Track grant of the Radboud University Medical Center (Nijmegen). The funders did not have any role in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study protocol was approved by the institutional review board of the University Medical Center Utrecht, the Netherlands, and, registered at [clinicaltrials.gov][1] (identifier: [NCT04328441][2]) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Individual participant data that underlie the results reported in this article will be made available after deidentification to investigators whose proposed use of the data has been approved by an independent review committee up to 5 years following publication. The study protocol will be available to anyone during this same time frame. Information regarding submitting proposals and accessing data may be found on . [1]: http://clinicaltrials.gov [2]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT04328441&atom=%2Fmedrxiv%2Fearly%2F2024%2F01%2F24%2F2024.01.24.24301644.atom