SARS-CoV-2 Antigen Rapid Detection Tests: test performance during the COVID-19 pandemic and the impact of COVID-19 vaccination (preprint)

IntroductionDuring the COVID-19 pandemic, SARS-CoV-2 antigen rapid detection tests (RDTs) emerged as point-of-care diagnostics in addition to the RT-qPCR as the gold standard for SARS-CoV-2 diagnostics. Facing the course of the COVID-19 pandemic to an endemic characterised by several SARS-CoV-2 virus variants of concern (VOC) and an increasing public COVID-19 vaccination rate the aim of the study was to investigate the long-term test performance of SARS-CoV-2 RDT in large-scale, clinical screening use during and its influencing factors, above all SARS-CoV-2 VOC and COVID-19 vaccination. MethodsIn a prospective performance assessment conducted at a single centre tertiary care hospital, RDTs from three manufacturers (NADAL(R), Panbio, MEDsan(R)) were compared to RT-qPCR among individuals aged [≥] 6 month. The evaluation involved the determination of standardised viral load from oropharyngeal swabs as well as the evaluation of their influencing factors, especially the COVID-19 vaccination, for detecting SARS-CoV-2 in a clinical point-of-care environment spanning from 12 November 2020 to 30 June 2023 among patients, staff, and visitors of the hospital. ResultsAmong the 78,798 RDT/RT-qPCR tandems analysed, 2,016 (2.6%) tandems tested positive for SARS-CoV-2, with an overall sensitivity of 34.5% (95% CI 32.4-36.6%). A logistic regression revealed that typical COVID-19 symptoms significantly declined over the course of the study and throughout the COVID-19 pandemic, and that among the vaccinated, significantly fewer presented with an infection exhibiting typical symptoms. The employed lasso regression model indicated that only higher viral load and typical COVID-19 symptoms significantly increase the likelihood of a positive RDT result in the case of a SARS-CoV-2 infection directly. ConclusionOur findings indicate that only viral load and COVID-19 symptoms directly influence RDT performance while the obtained effects of COVID-19 vaccination and Omicron VOC both reducing RDT performance were mediated by these two factors. RDTs remain an adequate diagnostic tool for detecting SARS-CoV-2 in individuals showing respiratory symptoms. RDTs show promise beyond SARS-CoV-2, proving adaptable for detecting other pathogens like Influenza and RSV, highlighting their ongoing importance in infection control and prevention efforts.

Examination of Influenza A Infection Rate, Its Determinants, and Seasonal Influenza Vaccine Effectiveness in the Post-COVID-19 Pandemic Era (preprint)

BackgroundIn the context of the COVID-19 pandemic, a pronounced wave of Influenza A occurred in the 2022/23 winter season under generally relaxed post-pandemic non-pharmaceutical preventive measures. AimThis study aimed to investigate the Influenza A infection rate, factors influencing its occurrence and seasonal Influenza vaccine effectiveness on seroconversion in the post-COVID-19 pandemic era. MethodsThe seroconversion of Anti-Influenza-A-Nucleoprotein/Matrix IgG was investigated in 402 healthcare workers (HCWs) during the winter season of 2022/2023 (23 May 2022 to 11 May 2023). The participants provided a serum sample and completed a study questionnaire both before and after the seasonal Influenza A wave (24 October 2022 to 8 January 2023). The levels of a vaccine-independent Anti-Influenza-A-Nucleoprotein/Matrix IgG were measured using the SERION ELISA classic Influenza A IgG assay, with a 2-fold increase as indicative of seroconversion after asymptomatic or symptomatic influenza infection. ResultsAmong the participants, 20.6% (95% CI 17.0-24.9%; 83/402) showed seroconversion. The multivariate logistic regression analysis revealed that the age category of [≥] 45 years (p=0.03) and regular patient contact (p=0.02) significantly influenced seroconversion. However, the factors male gender, BMI, smoking, household size, seasonal Influenza vaccination, and SARS-CoV-2 infection during the Influenza A season were not significantly associated with seroconversion. The effectiveness of the 2022/23 seasonal Influenza vaccine on seroconversion induced by Influenza infection was 22.6% (95% CI -17.1-50.6%). ConclusionDuring the initial Influenza A season following the COVID-19 pandemic, approximately 20% of HCWs contracted an Influenza A infection. This highlights a potential risk and a significant asymptomatic or symptomatic infection rate posing a theoretical risk for intrahospital transmission chains and nosocomial infections.

Estimates of protection against SARS-CoV-2 infection and severe COVID-19 in Germany before the 2022/2023 winter season - the IMMUNEBRIDGE project (preprint)

Despite the need to generate valid and reliable estimates of protection against SARS-CoV-2 infection and severe course of COVID-19 for the German population in summer 2022, there was a lack of systematically collected population-based data allowing for the assessment of the protection level in real-time. In the IMMUNEBRIDGE project, we harmonised data and biosamples for nine population-/hospital-based studies (total number of participants n=33,637) to provide estimates for protection levels against SARS-CoV-2 infection and severe COVID-19 between June and November 2022. Based on evidence synthesis, we formed a combined endpoint of protection levels based on the number of self-reported infections/vaccinations in combination with nucleocapsid/spike antibody responses ("confirmed exposures"). Four confirmed exposures represented the highest protection level, and no exposure represented the lowest. Most participants were seropositive against the spike antigen; 37% of the participants [≥]79 years had less than four confirmed exposures (highest level of protection) and 5% less than three. In the subgroup of participants with comorbidities, 46-56% had less than four confirmed exposures. We found major heterogeneity across federal states, with 4%-28% of participants having less than three confirmed exposures. Using serological analyses, literature synthesis and infection dynamics during the survey period, we observed moderate to high levels of protection against severe COVID-19, whereas the protection against SARS-CoV-2 infection was low across all age groups. We found relevant protection gaps in the oldest age group and amongst individuals with comorbidities, indicating a need for additional protective measures in these groups.

Clinical accuracy of SARS-CoV-2 rapid antigen testing in screening children and adolescents in comparison to RT-qPCR, November 2020 to September 2022 (preprint)

Background Rapid antigen detection tests (RDT) are an easily accessible, feasible, inexpensive, and point of care method in SARS-CoV-2 diagnostics - established in adults as well as in children and adolescents. Despite this, large-scale data of clinical performance in the paediatric population especially regarding the influence of SARS-CoV-2 virus variants of concern (VOC) and COVID-19 vaccination on test accuracy is rare. Methods This single centre prospective diagnostic study evaluates three RDT (NADAL(R), Panbio, MEDsan(R)) in comparison to quantitative reverse transcription polymerase chain reaction (RT-qPCR). 9,760 oropharyngeal screening samples regarding SARS-CoV-2 VOC and COVID-19 vaccination in paediatric hospitalised patients aged younger than 18 years were enrolled. Findings RDT sensitivity was 44{middle dot}7% (157/351, 95% CI 39{middle dot}6%-50{middle dot}0%) compared to the reference standard RT-qPCR, specificity 99{middle dot}8% (9,392/9,409, 95% CI 99{middle dot}7%-99{middle dot}9%). Most SARS-CoV-2 infections considered were caused by Omicron VOC. Diagnostic accuracy of RDT depended on specimen containing viral load with a decreasing RDT sensitivity by descending viral load, corresponding with a significantly impaired sensitivity in asymptomatic children. A sensitivity of 71{middle dot}0% was obtained for a viral load higher than 106 SARS-CoV-2 RNA copies per ml suggested as infectivity threshold. No significant differences in RDT sensitivity could be observed regarding gender, symptoms, COVID-19 vaccination status, and VOC. Interpretation In a paediatric population, RDT have proven to reliably detect potentially highly infectious patients with a viral load of at least 106 SARS-CoV-2 RNA copies per ml. Due to the low sensitivity in asymptomatic individuals, the usefulness of RDT seems limited in large scale SARS-CoV-2 screening programs. Funding Federal Ministry for Education and Science (BMBF), Free State of Bavaria

SARS-CoV-2 surveillance (09/2020 - 03/2021) in elementary schools and daycare facilities in Bavaria (preprint)

Here we report our results of a multi-center, open cohort study ("COVID-Kids-Bavaria") investigating the distribution of SARS-CoV-2 among children and staff in 99 daycare facilities and 48 elementary schools in Bavaria, Germany. Overall, 2568 children (1337 school children, 1231 preschool children) and 1288 adults (466 teachers, 822 daycare staff) consented to participate in the study and were randomly tested in three consecutive phases (September/October 2020, November/December 2020, March 2021). In total, 7062 throat swabs were analyzed for SARS-CoV-2 by RT-PCR. In phase I, only one daycare worker tested positive. In phase II, SARS-CoV-2 was detected in three daycare workers, two preschool children, and seven school children. In phase III, no sample tested positive. This corresponds to a positive test rate of 0.05% in phase I, 0.4% in phase II and 0% in phase III. After phase III, antibody testing was offered to 713 study participants in elementary schools. A seroprevalence rate of 7.7% (students) and 4.5% (teachers) was determined. We conclude that during the initial waves of the SARS-CoV-2 pandemic, the risk of a positive SARS-CoV-2 result correlated positively with the local 7-day incidence. Thus, an increased risk of SARS-CoV-2 transmission in the setting of daycare and elementary schooling was unlikely.

SARS-CoV-2 Antibodies in Children: A One-Year Seroprevalence Study From June 2020 to May 2021 in Germany (preprint)

Background: Investigating the role of children in the COVID-19 pandemic is pivotal to prevent the virus spreading. In most cases, children infected with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) develop non-specific symptoms or are asymptomatic. Therefore, the infection rate among this age group remains unclear. Seroprevalence studies, including clinical questionnaires, may contribute to our understanding of the time course and clinical manifestations of SARS-CoV-2 infections.Methods: SARS-CoV-2-KIDS is a longitudinal, hospital-based, multicentre study in Germany on the seroprevalence of anti-SARS-CoV-2 immunoglobulin G, as determined by an Enzyme-Linked Immunosorbent Assay in children (aged ≤17 years). A study-specific questionnaire provided additional information on clinical aspects.Findings: This analysis included 10,358 participants recruited from June 2020 to May 2021. The estimated anti-SARS-CoV-2 seroprevalence increased from 2·0% (95% confidence interval (95% CI) 1·6, 2·5) to 10·8% (95% CI 8·7, 12·9) in March 2021, without major change afterwards and was higher in children with migrant background (on average 6·6% vs. 2·8%). In the pandemic early stages, children under three years were 3·5 (95% CI 2·2, 5·6) times more likely to be seropositive than older children, with the levels equalising in later observations. History of self-reported respiratory tract infections or pneumonia was associated with seropositivity (OR 1·8 (95% CI 1·4, 2·3); 2·7 (95% CI 1·7, 4·1)).Interpretation: The majority of children in Germany do not have detectable SARS-CoV-2 IgG. To some extent, this may reflect the effect of differing containment measures implemented in the federal states. Detection levels might have been greater in certain age groups or migrant background. Lifting containment measurements is likely to cause a general increase in respiratory tract infections, which already pose a challenge to paediatric medical care during regular winter seasons. This challenge might become critical with additional infections caused by SARS-CoV-2.Funding: Funding Information: German Federal Ministry of Education and Research.Declaration of Interests: Authors have no conflicts of interest to declare.Ethics Approval Statement: Ethics committees of each study centre independently approved the study protocol. All parents/guardians gave written informed consent and children assented to the participation when appropriate for their age.

Clinical performance evaluation of SARS-CoV-2 rapid antigen testing in point of care usage in comparison to RT-qPCR (preprint)

Background Antigen rapid diagnostic tests (RDT) for SARS-CoV-2 are fast, broadly available, and inexpensive. Despite this, reliable clinical performance data is sparse. Methods In a prospective performance evaluation study, RDT from three manufacturers (NADAL, Panbio, MEDsan) were compared to quantitative reverse transcription polymerase chain reaction (RT-qPCR) in 5 068 oropharyngeal swabs for detection of SARS-CoV-2 in a hospital setting. Viral load was derived from standardized RT-qPCR Cycle threshold (Ct) values. The data collection period ranged from November 12, 2020 to February 28, 2021. Findings Overall, sensitivity of RDT compared to RT-qPCR was 42.57% (95% CI 33.38%-52.31%), and specificity 99.68% (95% CI 99.48%-99.80%). Sensitivity declined with decreasing viral load from 100% in samples with a deduced viral load of 10^8 SARS-CoV-2 RNA copies per ml to 8.82% in samples with a viral load lower than 104 SARS-CoV-2 RNA copies per ml. No significant differences in sensitivity or specificity could be observed between the three manufacturers, or between samples with and without spike protein variant B.1.1.7. The NPV in the study cohort was 98.84%; the PPV in persons with typical COVID-19 symptoms was 97.37%, and 28.57% in persons without or with atypical symptoms. Interpretation RDT are a reliable method to diagnose SARS-CoV-2 infection in persons with high viral load. RDT are a valuable addition to RT-qPCR testing, as they reliably detect infectious persons with high viral loads before RT-qPCR results are available. Funding German Federal Ministry for Education and Science (BMBF), Free State of Bavaria