Nucleocapsid-specific T cell responses associate with control of SARS-CoV-2 in the upper airways before seroconversion.

Despite intensive research since the emergence of SARS-CoV-2, it has remained unclear precisely which components of the early immune response protect against the development of severe COVID-19. Here, we perform a comprehensive immunogenetic and virologic analysis of nasopharyngeal and peripheral blood samples obtained during the acute phase of infection with SARS-CoV-2. We find that soluble and transcriptional markers of systemic inflammation peak during the first week after symptom onset and correlate directly with upper airways viral loads (UA-VLs), whereas the contemporaneous frequencies of circulating viral nucleocapsid (NC)-specific CD4+ and CD8+ T cells correlate inversely with various inflammatory markers and UA-VLs. In addition, we show that high frequencies of activated CD4+ and CD8+ T cells are present in acutely infected nasopharyngeal tissue, many of which express genes encoding various effector molecules, such as cytotoxic proteins and IFN-γ. The presence of IFNG mRNA-expressing CD4+ and CD8+ T cells in the infected epithelium is further linked with common patterns of gene expression among virus-susceptible target cells and better local control of SARS-CoV-2. Collectively, these results identify an immune correlate of protection against SARS-CoV-2, which could inform the development of more effective vaccines to combat the acute and chronic illnesses attributable to COVID-19.

Impaired humoral immunity to BQ.1.1 in convalescent and vaccinated patients.

Determining SARS-CoV-2 immunity is critical to assess COVID-19 risk and the need for prevention and mitigation strategies. We measured SARS-CoV-2 Spike/Nucleocapsid seroprevalence and serum neutralizing activity against Wu01, BA.4/5 and BQ.1.1 in a convenience sample of 1,411 patients receiving medical treatment in the emergency departments of five university hospitals in North Rhine-Westphalia, Germany, in August/September 2022. 62% reported underlying medical conditions and 67.7% were vaccinated according to German COVID-19 vaccination recommendations (13.9% fully vaccinated, 54.3% one booster, 23.4% two boosters). We detected Spike-IgG in 95.6%, Nucleocapsid-IgG in 24.0%, and neutralization against Wu01, BA.4/5 and BQ.1.1 in 94.4%, 85.0%, and 73.8% of participants, respectively. Neutralization against BA.4/5 and BQ.1.1 was 5.6- and 23.4-fold lower compared to Wu01. Accuracy of S-IgG detection for determination of neutralizing activity against BQ.1.1 was reduced substantially. We explored previous vaccinations and infections as correlates of BQ.1.1 neutralization using multivariable and Bayesian network analyses. Given a rather moderate adherence to COVID-19 vaccination recommendations, this analysis highlights the need to improve vaccine-uptake to reduce the COVID-19 risk of immune evasive variants. The study was registered as clinical trial (DRKS00029414).

Immunological fingerprint in coronavirus disease-19 convalescents with and without post-COVID syndrome.

Background: Symptoms lasting longer than 12 weeks after severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) infection are called post-coronavirus disease (COVID) syndrome (PCS). The identification of new biomarkers that predict the occurrence or course of PCS in terms of a post-viral syndrome is vital. T-cell dysfunction, cytokine imbalance, and impaired autoimmunity have been reported in PCS. Nevertheless, there is still a lack of conclusive information on the underlying mechanisms due to, among other things, a lack of controlled study designs. Methods: Here, we conducted a prospective, controlled study to characterize the humoral and cellular immune response in unvaccinated patients with and without PCS following SARS-CoV-2 infection over 7 months and unexposed donors. Results: Patients with PCS showed as early as 6 weeks and 7 months after symptom onset significantly increased frequencies of SARS-CoV-2-specific CD4+ and CD8+ T-cells secreting IFNγ, TNF, and expressing CD40L, as well as plasmacytoid dendritic cells (pDC) with an activated phenotype. Remarkably, the immunosuppressive counterparts type 1 regulatory T-cells (TR1: CD49b/LAG-3+) and IL-4 were more abundant in PCS+. Conclusion: This work describes immunological alterations between inflammation and immunosuppression in COVID-19 convalescents with and without PCS, which may provide potential directions for future epidemiological investigations and targeted treatments.

Early intervention with azelastine nasal spray may reduce viral load in SARS-CoV-2 infected patients.

With the changing epidemiology of COVID-19 and its impact on our daily lives, there is still an unmet need of COVID-19 therapies treating early infections to prevent progression. The current study was a randomized, parallel, double-blind, placebo-controlled trial. Ninety SARS-CoV-2 positive patients were randomized into 3 groups receiving placebo, 0.02% or 0.1% azelastine nasal spray for 11 days, during which viral loads were assessed by quantitative PCR. Investigators assessed patients' status throughout the trial including safety follow-ups (days 16 and 60). Symptoms were documented in patient diaries. Initial viral loads were log10 6.85 ± 1.31 (mean ± SD) copies/mL (ORF 1a/b gene). After treatment, virus load was reduced in all groups (p < 0.0001) but was greater in the 0.1% group compared to placebo (p = 0.007). In a subset of patients (initial Ct < 25) viral load was strongly reduced on day 4 in the 0.1% group compared to placebo (p = 0.005). Negative PCR results appeared earlier and more frequently in the azelastine treated groups: being 18.52% and 21.43% in the 0.1% and 0.02% groups, respectively, compared to 0% for placebo on day 8. Comparable numbers of adverse events occurred in all treatment groups with no safety concerns. The shown effects of azelastine nasal spray may thus be suggestive of azelastine's potential as an antiviral treatment.Trial registration: The study was registered in the German Clinical Trial Register (DRKS-ID: DRKS00024520; Date of Registration in DRKS: 12/02/2021). EudraCT number: 2020-005544-34.

Primary ChAdOx1 vaccination does not reactivate pre-existing, cross-reactive immunity.

Currently available COVID-19 vaccines include inactivated virus, live attenuated virus, mRNA-based, viral vectored and adjuvanted protein-subunit-based vaccines. All of them contain the spike glycoprotein as the main immunogen and result in reduced disease severity upon SARS-CoV-2 infection. While we and others have shown that mRNA-based vaccination reactivates pre-existing, cross-reactive immunity, the effect of vector vaccines in this regard is unknown. Here, we studied cellular and humoral responses in heterologous adenovirus-vector-based ChAdOx1 nCOV-19 (AZ; Vaxzeria, AstraZeneca) and mRNA-based BNT162b2 (BNT; Comirnaty, BioNTech/Pfizer) vaccination and compared it to a homologous BNT vaccination regimen. AZ primary vaccination did not lead to measurable reactivation of cross-reactive cellular and humoral immunity compared to BNT primary vaccination. Moreover, humoral immunity induced by primary vaccination with AZ displayed differences in linear spike peptide epitope coverage and a lack of anti-S2 IgG antibodies. Contrary to primary AZ vaccination, secondary vaccination with BNT reactivated pre-existing, cross-reactive immunity, comparable to homologous primary and secondary mRNA vaccination. While induced anti-S1 IgG antibody titers were higher after heterologous vaccination, induced CD4+ T cell responses were highest in homologous vaccinated. However, the overall TCR repertoire breadth was comparable between heterologous AZ-BNT-vaccinated and homologous BNT-BNT-vaccinated individuals, matching TCR repertoire breadths after SARS-CoV-2 infection, too. The reasons why AZ and BNT primary vaccination elicits different immune response patterns to essentially the same antigen, and the associated benefits and risks, need further investigation to inform vaccine and vaccination schedule development.

Short- and long-term T cell and antibody responses following dexamethasone treatment in COVID-19.

BACKGROUNDAfter its introduction as standard-of-care for severe COVID-19, dexamethasone has been administered to a large number of patients globally. Detailed knowledge of its impact on the cellular and humoral immune response to SARS-CoV-2 remains scarce.METHODSWe included immunocompetent individuals with (a) mild COVID-19, (b) severe COVID-19 before introduction of dexamethasone treatment, and (c) severe COVID-19 infection treated with dexamethasone from prospective observational cohort studies at Charité-Universitätsmedizin Berlin, Germany. We analyzed SARS-CoV-2 spike-reactive T cells, spike-specific IgG titers, and serum neutralizing activity against B.1.1.7 and B.1.617.2 in samples ranging from 2 weeks to 6 months after infection. We also analyzed BA.2 neutralization in sera after booster immunization.RESULTSPatients with severe COVID-19 and dexamethasone treatment had lower T cell and antibody responses to SARS-CoV-2 compared with patients without dexamethasone treatment in the early phase of disease, which converged in both groups before 6 months after infection and also after immunization. Patients with mild COVID-19 had comparatively lower T cell and antibody responses than patients with severe disease, including a lower response to booster immunization during convalescence.CONCLUSIONDexamethasone treatment was associated with a short-term reduction in T cell and antibody responses in severe COVID-19 when compared with the nontreated group, but this difference evened out 6 months after infection. We confirm higher cellular and humoral immune responses in patients after severe versus mild COVID-19 and the concept of improved hybrid immunity upon immunization.FUNDINGBerlin Institute of Health, German Federal Ministry of Education, and German Federal Institute for Drugs and Medical Devices.

Morbidity of Respiratory Syncytial Virus-infections (RSV): RSV compared with SARS-CoV-2 infections in children aged 0 - 4 years in Cologne, Germany.

The aim of this retrospective analysis was to provide information on how infections with RSV and SARS-CoV-2 differ in symptoms, clinical course, outcome and the utilization of hospital care. We investigated 748 PCR results from symptomatic children aged 0 - 4 years in Cologne, Germany. 169 patients were tested positive for RSV (22.6%) and 24 children for SARS-CoV-2 (3.2%). Symptomatic patients with RSV-infection were hospitalized significantly longer. RSV-positive patients needed O2-supplementation significantly more often as well as High Flow-therapy. With regard to care efforts, RSV-infected patients put higher pressure on the hospital and utilized more hospital resources.

Implementing the Lolli-Method and pooled RT-qPCR testing for SARS-CoV-2 surveillance in schools: a pilot project.

PURPOSE: School closures have been used as part of lockdown strategies to contain the spread of SARS-CoV-2, adversely affecting children's health and education. To ensure the accessibility of educational institutions without exposing society to the risk of increased transmissions, it is essential to establish SARS-CoV-2 testing strategies that are child-friendly, scalable and implementable in a daily school routine. Self-sampling using non-invasive saliva swabs combined with pooled RT-qPCR testing (Lolli-Method) has been proven to be a sensitive method for the detection of SARS-CoV-2. METHODS: We conducted a pilot project in Cologne, Germany, designed to determine the feasibility of a large-scale rollout of the Lolli-Method for testing without any additional on-site medical staff in schools. Over a period of three weeks, students from 22 schools were sampled using the Lolli-Method. At the end of the project, teachers were asked to evaluate the overall acceptance of the project. RESULTS: We analyzed a total of 757 pooled RT-qPCRs obtained from 8,287 individual swabs and detected 7 SARS-CoV-2 infected individuals. The Lolli-Method was shown to be a feasible and accepted testing strategy whose application is only slightly disruptive to the daily school routine. CONCLUSION: Our observations suggest that the Lolli-Method in combination with pooled RT-qPCR can be implemented for SARS-CoV-2 surveillance in daily school routine, applicable on a large scale.

Boosting compromised SARS-CoV-2-specific immunity with mRNA vaccination in liver transplant recipients.

BACKGROUND & AIMS: Liver transplant recipients (LTRs) demonstrate a reduced response to COVID-19 mRNA vaccination; however, a detailed understanding of the interplay between humoral and cellular immunity, especially after a third (and fourth) vaccine dose, is lacking. METHODS: We longitudinally compared the humoral, as well as CD4+ and CD8+ T-cell, responses between LTRs (n = 24) and healthy controls (n = 19) after three (LTRs: n = 9 to 16; healthy controls: n = 9 to 14 per experiment) to four (LTRs: n = 4; healthy controls: n = 4) vaccine doses, including in-depth phenotypical and functional characterization. RESULTS: Compared to healthy controls, development of high antibody titers required a third vaccine dose in most LTRs, while spike-specific CD8+ T cells with robust recall capacity plateaued after the second vaccine dose, albeit with a reduced frequency and epitope repertoire compared to healthy controls. This overall attenuated vaccine response was linked to a reduced frequency of spike-reactive follicular T helper cells in LTRs. CONCLUSION: Three doses of a COVID-19 mRNA vaccine induce an overall robust humoral and cellular memory response in most LTRs. Decisions regarding additional booster doses may thus be based on individual vaccine responses as well as evolution of novel variants of concern. IMPACT AND IMPLICATIONS: Due to immunosuppressive medication, liver transplant recipients (LTR) display reduced antibody titers upon COVID-19 mRNA vaccination, but the impact on long-term immune memory is not clear. Herein, we demonstrate that after three vaccine doses, the majority of LTRs not only exhibit substantial antibody titers, but also a robust memory T-cell response. Additional booster vaccine doses may be of special benefit for a small subset of LTRs with inferior vaccine response and may provide superior protection against evolving novel viral variants. These findings will help physicians to guide LTRs regarding the benefit of booster vaccinations.

Results of the Cologne Corona Surveillance (CoCoS) study - a cross-sectional study: survey data on risk factors of SARS-CoV-2 infection in adults.

BACKGROUND: The personal, environmental, and behavioral risk factors that play an important role in the spread of SARS-CoV-2 are still largely unclear. At the same time, there is limited evidence on the effectiveness of specific countermeasures for SARS-CoV-2. As a first approach to these questions, we use data from the Cologne Corona Surveillance (CoCoS) study, a large cross-sectional study conducted in Cologne, Germany, in June 2021. METHODS: This study was conducted in Cologne, Germany. Six thousand randomly selected Cologne residents who were 18 years of age or older were invited to participate in this study. Participant information was obtained via an online survey. Previous SARS-CoV-2 infections were recorded using self-reports. Sociodemographic and environmental information such as age, sex, living situation were collected. Potential SARS-CoV-2 risk behaviors were captured (workplace situation, adherence to hygiene regulations, and regular use of public transportation). Adherence to hygiene regulations was surveyed by determining the compliance with the 'AHA'-rules (German acronym that stands for keeping a distance of 1.5 m from fellow citizens, hand disinfection, and wearing a face mask). Binary logistic regression analysis was used to identify risk factors for SARS-CoV-2 infection. RESULTS: A sample of 2,433 study participants provided information. Comparison of the sample with the general population showed representativeness for most sociodemographic characteristics with a preference for higher level of education in the study sample. Younger age, as well as living with minor children (under 18 years) in the same household were associated with a higher number of self-reported SARS-CoV-2 infections. Adherence to hygiene regulations was associated with fewer self-reported SARS-CoV-2 infections in adults. Gender, size of living space per person, workplace situation (work from home versus working with contact to colleagues/customers), and regular use of public transportation showed no significant association with self-reported SARS-CoV-2 infections in multivariable analysis. CONCLUSION: The presented results provide initial indications of which sociodemographic and behavioral factors may be associated with SARS-CoV-2 infection. However, the fact that these factors were recorded without exact dates and could have changed accordingly during the pandemic or after infection limits the strength of the results. TRIAL REGISTRATION: DRKS.de, German Clinical Trials Register (DRKS), Identifier: DRKS00024046, Registered on 25 February 2021.

Rapid selection of sotrovimab escape variants in SARS-CoV-2 Omicron infected immunocompromised patients.

BACKGROUND: Monoclonal antibodies (mAb) targeting SARS-CoV-2 are predominantly less effective against Omicron variants. Immunocompromised patients often experience prolonged viral shedding and are therefore at increased risk for viral escape mutations, when mAbs are used as monotherapy. METHODS: In an observational, prospective cohort, 57 patients infected with Omicron variants receiving sotrovimab alone or in combination with remdesivir were followed. The study endpoints were a decrease in SARS-CoV-2-RNA <106 copies/ml in nasopharyngeal swabs at day 21 and the emergence of resistance mutations at days 7, 14, and 21 after sotrovimab administration. All SARS-CoV-2 samples were analyzed by whole-genome sequencing, individual variants within the quasispecies were subsequently quantified and further characterized by a pseudovirus neutralization assay. RESULTS: 47/57 patients (82.5%) were infected with Omicron/BA.1 and 10/57 (17.5%) with Omicron/BA.2. The vast majority of patients (43/57, 75.4%) were immunodeficient, predominantly due to immunosuppression after organ transplantation or hematologic malignancies. 21 days after sotrovimab administration, 12/43 (27.9%) of immunodeficient patients had prolonged viral shedding compared to 1/14 (7.1%) immunocompetent patients (p = 0.011). Longitudinal sequencing revealed that 14/43 (32.6%) immunodeficient patients had in part Omicron-specific viral spike protein mutations (e.g., P337S and/or E340D/V) that substantially reduced susceptibility to sotrovimab in a pseudovirus neutralization assay. Combination therapy with remdesivir significantly reduced the selection of escape variants. CONCLUSIONS: Immunocompromised patients face a considerable risk of prolonged viral shedding and emergence of escape mutations after early therapy with sotrovimab. These findings underscore the importance of careful monitoring and the need to conduct dedicated clinical trials for this patient population.

Immune Response to Third and Fourth COVID-19 Vaccination in Hemodialysis Patients and Kidney Transplant Recipients.

Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is a serious hazard for hemodialysis (HD) patients and kidney transplant (KTX) recipients as they suffer from an impaired immune response to SARS-CoV-2 vaccination. In addition, a definition of SARS-CoV-2 IgG titer that indicates a sufficient immune response, especially against new omicron variants, is urgently needed. In the present study, the immune response to either a third or a fourth dose of a mRNA vaccine was investigated in 309 dialysis and 36 KTX patients. SARS-CoV-2 IgG titer thresholds indicating neutralizing activity against wild type (WT) and the omicron variant BA.1 were quantified. After four vaccine doses, a high-neutralizing activity against WT was evidenced in HD patients, whereas the neutralizing rate against BA.1 was significant lower. Concerning KTX recipients, humoral and cellular immune responses after a third vaccination were still highly impaired. This calls for modified omicron-targeting vaccines.

Pausing methotrexate prevents impairment of Omicron BA.1 and BA.2 neutralisation after COVID-19 booster vaccination.

OBJECTIVE: The level of neutralising capacity against Omicron BA.1 and BA.2 after third COVID-19 vaccination in patients on paused or continuous methotrexate (MTX) therapy is unclear. METHODS: In this observational cohort study, neutralising serum activity against SARS-CoV-2 wild-type (Wu01) and variant of concern Omicron BA.1 and BA.2 were assessed by pseudovirus neutralisation assay before, 4 and 12 weeks after mRNA booster immunisation in 50 rheumatic patients on MTX, 26 of whom paused the medication. 44 non-immunosuppressed persons (NIP) served as control group. RESULTS: While the neutralising serum activity against SARS-CoV-2 Wu01 and Omicron variants increased 67-73 fold in the NIP after booster vaccination, the serum activity in patients receiving MTX increased only 20-23 fold. Patients who continued MTX treatment during vaccination had significantly lower neutralisation against all variants at weeks 4 and 12 compared with patients who paused MTX and the control group, except for BA.2 at week 12. Patients who paused MTX reached comparably high neutralising capacities as NIP, except for Wu01 at week 12. The duration of the MTX pause after-not before-was associated with a significantly higher neutralisation capacity against all three variants, with an optimal duration at 10 days after vaccination. CONCLUSION: Patients pausing MTX after COVID-19 booster showed a similar vaccine response to NIP. Patients who continued MTX demonstrated an impaired response indicating a potentially beneficial second booster vaccination. Our data also suggest that a 1 week MTX break is sufficient if the last administration of MTX occurs 1-3 days before vaccination.

SARS-CoV-2 Omicron sublineages exhibit distinct antibody escape patterns.

SARS-CoV-2 neutralizing antibodies play a critical role in COVID-19 prevention and treatment but are challenged by viral evolution and the emergence of novel escape variants. Importantly, the recently identified Omicron sublineages BA.2.12.1 and BA.4/5 are rapidly becoming predominant in various countries. By determining polyclonal serum activity of 50 convalescent or vaccinated individuals against BA.1, BA.1.1, BA.2, BA.2.12.1, and BA.4/5, we reveal a further reduction in BA.4/5 susceptibility to vaccinee sera. Most notably, delineation of sensitivity to an extended 163-antibody panel demonstrates pronounced antigenic differences with distinct escape patterns among Omicron sublineages. Antigenic distance and/or higher resistance may therefore favor immune-escape-mediated BA.4/5 expansion after the first Omicron wave. Finally, while most clinical-stage monoclonal antibodies are inactive against Omicron sublineages, we identify promising antibodies with high pan-SARS-CoV-2 neutralizing potency. Our study provides a detailed understanding of Omicron-sublineage antibody escape that can inform on effective strategies against COVID-19.

Viral Load Dynamics in SARS-CoV-2 Omicron Breakthrough Infections.

To determine viral dynamics in Omicron breakthrough infections, we measured severe acute respiratory syndrome coronavirus 2 RNA in 206 double-vaccinated or boostered individuals. During the first 3 days following the onset of symptoms, viral loads were significantly higher (cycle threshold [Ct], 21.76) in vaccinated compared to boostered (Ct, 23.14) individuals (P = .029). However, by performing a longitudinal analysis on 32 individuals over 14 days, no difference in the viral load trajectory was observed between double-vaccinated and boostered patients. Our results indicate that booster immunization results in a reduction in detectable viral loads without significantly changing viral load dynamics over time.

Clinical Aspects of the Subsequent SARS-CoV-2 Waves in Children from 2020 to 2022-Data from a Local Cohort in Cologne, Germany (n = 21,635).

Almost two and a half years after the appearance of the first cases of SARS-CoV-2 in December 2019, more than 500 million people have been infected with SARS-CoV-2 and over 6 million have died of it worldwide. In terms of the pediatric cohort, it already became evident at an early stage that the infection causes milder symptoms in children and rarely runs a fatal course. OBJECTIVE: This work presents data gathered over a period of over two years in patients between the age of 0 and 18 years. The aim is to provide information on the clinical aspects of the five different SARS-CoV-2 waves. METHODS: Between 13 March 2020 and 22 April 2022, all nucleic acid amplification tests (NAATs) of children who received a swab for SARS-CoV-2 at our clinic were included. Data were collected on standardized questionnaires. The analysis of the data was anonymized and retrospective. RESULTS: We investigated 21,635 NAATs, of which 1028 of the tests were positive (4.8%). The highest rate of positive results was observed in the fifth wave (541/2.292 NAATs (23.6%)). Most of the children who were hospitalized were hospitalized in wave three (22.9%). The availability of a vaccine was followed by a decrease in positive NAATs in the corresponding age group thereafter. CONCLUSIONS: These data underline the fact that children infected with SARS-CoV-2, regardless of which VOC, are often only mildly affected. Vaccinations seem to remain the key to avoid massive numbers of infected people and a potential collapse of the healthcare systems.

Results of the Cologne Corona surveillance (CoCoS) study - a prospective population-based cohort study: incidence data and potential underestimation of new SARS-CoV-2 adult infections by health authorities.

BACKGROUND: Current incidence estimates of SARS-CoV-2 in Germany rely to a large extent on case notifications. However, the large number of mild or asymptomatic infections is likely to result in underestimation. Population-based studies can provide valid estimates of the SARS-CoV-2 incidence and thus support health authorities to monitor the epidemiological situation and to initiate, maintain, strengthen or relax effective countermeasures. METHODS: This study was conducted in Cologne, Germany. Six-thousand randomly drawn Cologne residents, 18 years of age or older, were contacted by mail in March 2021. Study envelopes contained a kit for self-administered saliva sample and access details to a questionnaire on sociodemographic characteristics, previous positive SARS-CoV-2 RT-qPCR and completed COVID-19 vaccinations. Participants were again invited for a second round in June 2021, while those who declined participation were replaced by additional randomly drawn Cologne residents in order to reach a total of 6000 potential participants again. The saliva samples were sent to the laboratory by mail and tested for SARS-CoV-2 using RT-qPCR. The incidence estimates were adjusted for sensitivity and specificity of the test procedure and compared with the official numbers of new SARS-CoV-2 cases in the adult Cologne population. RESULTS: The first surveillance round in March 2021 (response rate: 34.08%, N = 2045) showed a SARS-CoV-2 seven-day incidence of 85 cases per 100,000 adult Cologne residents (95% CI: 9 to 319). In the same period, the officially registered cases were 125 per 100,000. The second surveillance round in June 2021 (response rate: 36.53%, N = 2192) showed a seven-day incidence of 27 per 100,000 adult Cologne residents (95% CI: 1 to 142), while the official figures for newly registered SARS-CoV-2 cases in the same period were 15 per 100,000. CONCLUSIONS: The incidence estimates do not indicate relevant underestimation of new SARS-CoV-2 infections based on case notification. Regular use of the surveillance method developed here may nevertheless complement the efforts of the health authorities to assess the epidemiological situation. TRIAL REGISTRATION: DRKS.de, German Clinical Trials Register (DRKS), Identifier: DRKS00024046 , Registered on 25 February 2021.