Results of WICOVIR Gargle Pool PCR Testing in German Schools Based on the First 100,000 Tests

Abstract

Background: Opening schools and keeping children safe from SARS-CoV-2 infections at the same time is urgently needed to protect children from direct and indirect consequences of the COVID-19 pandemic. To achieve this goal, a safe, efficient, and cost-effective SARS-CoV-2 testing system for schools in addition to standard hygiene measures is necessary. Methods: We implemented the screening WICOVIR concept for schools in the southeast of Germany, which is based on gargling at home, pooling of samples in schools, and assessment of SARS-CoV-2 by pool rRT-PCR, performed decentralized in numerous participating laboratories. Depooling was performed if pools were positive, and results were transmitted with software specifically developed for the project within a day. Here, we report the results after the first 13 weeks in the project. Findings: We developed and implemented the proof-of-concept test system within a pilot phase of 7 weeks based on almost 17,000 participants. After 6 weeks in the main phase of the project, we performed >100,000 tests in total, analyzed in 7,896 pools, identifying 19 cases in >100 participating schools. On average, positive children showed an individual CT value of 31 when identified in the pools. Up to 30 samples were pooled (mean 13) in general, based on school classes and attached school staff. All three participating laboratories detected positive samples reliably with their previously established rRT-PCR standard protocols. When self-administered antigen tests were performed concomitantly in positive cases, only one of these eight tests was positive, and when antigen tests performed after positive pool rRT-PCR results were already known were included, 3 out of 11 truly positive tests were also identified by antigen testing. After 3 weeks of repetitive WICOVIR testing twice weekly, the detection rate of positive children in that cohort decreased significantly from 0.042 to 0.012 (p = 0.008). Interpretation: Repeated gargle pool rRT-PCR testing can be implemented quickly in schools. It is an effective, valid, and well-received test system for schools, superior to antigen tests in sensitivity, acceptance, and costs.

Keywords: COVID-19; Germany; PCR; children; gargle; pandemic; pooling; schools.

Figure 1

Map of Bavarian counties participating in WICOVIR as of May 15, 2021.

Figure 2

Study design and numbers of the WICOVIR study as of May 12, 2021. *Participant numbers change over time, as new schools were included and some schools/individuals may have dropped out while others joined. **In pilot the phase, we explored teacher pools (as no clearance for student tests was yet available) and allowed family members of teachers to participate in these teacher pools.

Figure 3

Sample/data flow and data protection. Student samples were pooled in the participating schools, who kept analog records of pool participants and registered pools in the software. Pools were barcoded and sent to the lab. Pool test results were documented in the software by the lab and schools received results through the software. In the case of a positive pool, individual samples pertaining to a positive pool were sent to the lab and individual results were entered into the software in a pseudonymized fashion. Health authorities had access to the pseudonymized data in the software and received personalized results directly from the labs through official reporting software.

Figure 4

Development of test and pool numbers in the pilot and main phase of the WICOVIR project and positive results of testings per week.

Figure 5

Indicators of acceptance of antigen tests and gargle pool PCR tests in schools based on 71 responses from school heads (74% participation rate).