PERSISTENT IMMUNITY AFTER MILD SARS CoV-2 INFECTION - THE CoNAN-LONG TERM STUDY -

Objectives Understanding persistent cellular and humoral immune responses to SARS-CoV-2 will be of major importance to terminate the ongoing pandemic. Here we assessed long-term immunity in individuals with mild COVID-19 up to one year after a localized SARS-CoV-2 outbreak. Methods CoNAN was a longitudinal population-based cohort study performed 1.5 months, 6 months and 12 months after a SARS-CoV-2 outbreak in a rural German community. We performed a time series of five different IgG immunoassays assessing SARS-CoV-2 antibody responses on serum samples from individuals that had been tested positive after a SARS-CoV-2 outbreak as well as in control individuals who had a negative PCR result. These analyses were complemented with the determination of spike-antigen specific TH cell responses in the same individuals. Results All infected participants presented as asymptomatic or mild cases. Participants initially tested positive for SARS-CoV-2 infection either with PCR, antibody testing, or both had a rapid initial decline in the serum antibody levels in all serological test but showed a persisting and robust TH cell immunity as assessed by the detection of SARS-CoV-2 specificity of TH cells for up to one year after infection. Conclusion Our data support the notion of a robust T cell immunity in mild and asymptomatic cases of SARS-CoV-2 up to one year after infection. We show that antibody titers decline over one year, but considering several test results, complete seroconversion is rare. Trial Registration German Clinical Trials Register DRKS00022416. Funding Sondervermögen „Corona” of the Thuringian Ministry for Economic Affairs, Science and Digital Society. SV-Kapitel 82 30 Titel 68205 # 5526/32-4-2. ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Trial DRKS00022416 ### Funding Statement CoNAN was funded by the Sondervermoegen Corona of the Thuringian Ministry for Economic Affairs, Science and Digital Society (TMWWDG). ### 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 was conducted according to the current version of the Declaration of Helsinki and has been approved by the institutional ethics committees of the Jena University Hospital and the respective data protection commissioner (approval number 2020-1776) and the ethics committee of the Thuringian chamber of physicians. All data were collected with unique pseudonyms on paper case report forms. These identifiers were later used to merge the questionnaire information with the laboratory information in an electronic study database. The study is registered at the German Clinical Trials Register: DRKS00022416. 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 and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present work are contained in the manuscript