ABSTRACT
ObjectivesUnderstanding 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. MethodsCoNAN 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. ResultsAll 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. ConclusionOur 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 RegistrationGerman Clinical Trials Register DRKS00022416. FundingSondervermogen "Corona" of the Thuringian Ministry for Economic Affairs, Science and Digital Society. SV-Kapitel 82 30 Titel 68205 # 5526/32-4-2.
ABSTRACT
BackgroundDue to the substantial proportion of asymptomatic and mild courses many SARS-CoV-2 infections remain unreported. Therefore, assessment of seroprevalence may detect the real burden of disease. We aimed at determining and characterizing the rate of SARS-CoV-2 infections and the resulting immunity in a defined population. MethodsCoNAN is a population-based cohort study in the previously quarantined community Neustadt-am-Rennsteig, Germany six weeks after a SARS-CoV-2 outbreak with 49 cases identified by PCR screening of all 883 inhabitants. The primary objective of the study was to assess SARS-CoV-2 antibody seroconversion rate using six different IgG detecting immunoassays. Secondary objectives of the study were: i.) to determine the rate of seroconversion in children; ii.) to determine potential risk factors for symptomatic vs. asymptomatic Covid19 courses; iii.) to investigate the rate of virus persistence. FindingsWe enrolled 626 participants (71% of the community population). All actual SARS-CoV-2 PCR tests were negative; while a total of 8{middle dot}4% (52 of 620 tested) had antibodies against SARS-CoV-2 in at least two independent tests. Twenty of the antibody positive participants had previously a positive SARS-CoV-2 PCR. On the contrary, of those 38 participants with SARS-CoV-2 infection, only 20 (52{middle dot}6%) were antibody positive. InterpretationSeveral antibody tests conducted six weeks after an outbreak of SARS-CoV-2 did not detect all previously PCR-positive tested individuals. Cautious evaluation of antibody testing strategies to assess immunity against the infection is warranted. FundingCoNAN was funded by the Thuringian Ministry for Economic Affairs, Science and Digital Society (TMWWDG).
