ABSTRACT
Background and Objectives Test-to-stay concepts apply serial testing of children in daycare after exposure to SARS-CoV-2 without use of quarantine. This study aims to assess safety of a test-to-stay screening in daycare facilities. Methods 714 daycare facilities and approximately 50,000 children [≤]6 years in Cologne, Germany participated in a SARS-CoV-2 Pool-PCR screening from March 2021 to April 2022. The screening initially comprised post-exposure quarantine and was adapted to a test-to-stay approach during its course. To assess safety of the test-to-stay approach, we explored potential changes in frequencies of infections among children following the adaptation to the test-to-stay approach by applying regression discontinuity in time (RDiT) analyses. To this end, PCR-test data were linked with routinely collected data on reported infections in children and analyzed using ordinary least squares regressions. Results 219,885 Pool-PCRs and 352,305 Single-PCRs were performed. 6,440 (2.93%) Pool-PCRs tested positive, and 17,208 infections in children were reported. We estimated that during a period of 30 weeks, the test-to-stay concept avoided between 7 and 20 days of quarantine per eligible daycare child. RDiT revealed a 26% reduction (Exp. Coef: 0.74, CI:0.52;1.06) in infection frequency among children and indicated no significant increase attributable to the test-to-stay approach. This result was not sensitive to adjustments for 7-day incidence, season, SARS-CoV-2 variant, and socioeconomic status. Conclusion Our analyses provide evidence that suggest safety of the test-to-stay approach compared to traditional quarantine measures. This approach offers a promising option to avoid use of quarantine after exposure to respiratory pathogens in daycare settings.
ABSTRACT
Systematic SARS-CoV-2 testing is a valuable tool for infection control and surveillance. However, broad application of high sensitive RT-qPCR testing in children is often hampered due to unpleasant sample collection, limited RT-qPCR capacities, and high costs. Here, we developed a high-throughput approach (Lolli-Method) for sensitive SARS-CoV-2 detection in children, combining non-invasive sample collection with an RT-qPCR-pool testing strategy. SARS-CoV-2 infections were diagnosed with sensitivities of 100% and 93.9% when viral loads were >10E6 copies/ml and >10E3 copies/ml in corresponding Naso-/Oropharyngeal-swabs, respectively. For effective application of the Lolli-Method in schools and daycare facilities, SIR-modeling indicated a preferred frequency of two tests per week. The developed test strategy was implemented in 3,700 schools and 698 daycare facilities in Germany, screening over 800,000 individuals twice per week. In a period of 3 months, 6,364 pool-RT-qPCRs tested positive (0.64%) ranging from 0.05% to 2.61% per week. Notably, infections correlated with local SARS-CoV-2 incidences as well as with a school social deprivation index. Moreover, in comparison with the alpha variant, statistical modeling revealed a 31% increase for multiple (>1 child) infections per class following infections with the delta variant. We conclude that the Lolli-Method is a powerful tool for SARS-CoV-2 surveillance and infection control in schools and daycare facilities.
Subject(s)
Sleep Deprivation , Severe Acute Respiratory Syndrome , COVID-19ABSTRACT
Background / Objectives: The global spread of SARS-CoV-2 is a serious public health issue. Large-scale surveillance screenings are crucial but can exceed diagnostic test capacities. We set out to optimize test conditions and implemented high throughput pool testing of respiratory swabs into SARS-CoV-2 diagnostics. Study design: In preparation for pool testing, we determined the optimal pooling strategy and pool size. In addition, we measured the impact of vortexing prior to sample processing, compared pipette- and swab-pooling method as well as the sensitivity of three different PCR assays. Results: Using optimized strategies for pooling, we systematically pooled 55,690 samples in a period of 44 weeks resulting in a reduction of 47,369 PCR reactions. In a low prevalence setting, we defined a preferable pool size of ten in a two-stage hierarchical pool testing strategy. Vortexing of the swabs increased cellular yield by a factor of 2.34, and sampling at or shortly after symptom onset was associated with higher viral loads. By comparing different pooling strategies, pipette-pooling was more efficient compared to swab-pooling. Conclusions: For implementing pooling strategies into high throughput diagnostics, we recommend to apply a pipette-pooling method, using pool sizes of ten samples, performing sensitivity validation of the PCR assays used, and vortexing swabs prior to analyses. Our data shows, that pool testing for SARS-CoV-2 detection is feasible and highly effective in a low prevalence setting.
ABSTRACT
We analysed SARS-CoV-2 specific antibody responses in 42 social and working contacts of a super-spreader from the Heinsberg area in Germany. Consistent with a high-prevalence setting 26 individuals had SARS-CoV-2 antibodies determined by in-house neutralisation testing. These results were compared with four commercial assays, suggesting limited sensitivity of the assays in such a high-prevalence setting. Although SARS-CoV-2 nucleocapsid-restricted tests showed a better sensitivity, spike-based assays had a stronger correlation with neutralisation capacity.