Saliva Sampling for Prospective SARS-CoV-2 Screening of Healthcare Professionals

SARS-CoV-2 Infection in Health Care Workers of Trieste (North-Eastern Italy), 1 October 2020–7 February 2022: Occupational Risk and the Impact of the Omicron Variant

Vaccination coverage against COVID-19 among health care workers (HCWs) of the University Health Agency Giuliano-Isontina (ASUGI) of Trieste (North-eastern Italy) by 1 January 2022 was 90.4% with at least one vaccine dose, 84.9% with at least 2 doses, and 75.1% with 3 doses, 98.2% with Comirnaty (Pfizer BioNtech, New York, NY, USA) versus 1.8% with Spikevax (Moderna, Cambridge, MA, USA). From 1 October 2020 to 7 February 2022, 1652 SARS-CoV-2 infections were notified in HCWs of ASUGI Trieste. Although the overall risk of SARS-CoV-2 contagion increased over time, the rate of occupational infections progressively declined, from 42.5% during the second COVID-19 wave to 15.6% in the fifth. Between 1 January–7 February 2022 (a period dominated by the Omicron variant), albeit no COVID-19-associated hospitalizations were recorded in HCWs of ASUGI Trieste, 669 SARS-CoV-2 infections were counted against 367 cases observed from 1 October to 31 December 2020, the 3 months preceding the implementation of the vaccination campaign against COVID-19. Job tasks and health care settings turned out to be the most significant risk factors for SARS-CoV-2 infection. However, the effect of workplace prevailed over job task on the biological risk, with greater rates of SARS-CoV-2 infections observed among HCWs operating in areas with higher levels of circulation of the virus, particularly COVID-19 dedicated units.

Gargle Pool PCR Testing in a Hospital during medium and high SARS-CoV-2 incidence

Background

Hospitals need to be protected from SARS-CoV-2 infections to protect vulnerable patients. Thus, a safe, efficient, and cost-effective SARS-CoV-2 testing system for hospitals, in addition to standard hygiene measures and vaccination of staff, is necessary. Here we report on the feasibility and performance of a pool real-time reverse-transcriptase polymerase-chain-reaction (rRT-PCR) test system at, medium and high incidence.

Methods

We implemented a testing concept based on gargling at home and pooling of samples in the hospital before PCR testing in the laboratory. We used two PCR systems (point of care and standard 96-well plate system) to adapt to challenges in the hospital setting and respond to a rising incidence in the Omicron wave.

Findings

During our 10-week study period, we performed 697 pool PCRs (8793 tests in total) and identified 65 asymptomatic staff members by pool PCR and 94 symptomatic staff members by positive individual PCR. Virus loads in those detected by pool testing were significantly lower (P<0.001). The test system remained workable even during the peak of the Omicron wave and no outbreaks occurred in any specific area of the hospital during the study period. Unvaccinated individuals were over-represented in the positively tested (37% vs 22% positive tests, P=0.04). The test procedure was well accepted by a majority of the hospital staff (84%).

Conclusion

Repeated gargle pool rRT-PCR testing can be implemented quickly in hospitals and is an effective, easily adaptable and well-accepted test system for hospitals, even during phases with very high infection rates.

Evaluation of water gargle samples for SARS-CoV-2 detection using Abbott ID NOW COVID-19 assay

The Abbott ID NOW™ COVID‐19 assay has been shown as a reliable and sensitive alternative to reverse transcription‐polymerase chain reaction (RT‐PCR) testing from nasopharyngeal or nasal samples in symptomatic patients. Water gargle is an acceptable noninvasive alternative specimen for severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) detection by RT‐PCR. The objective of this study was to evaluate the performance of water gargle samples for the detection of SARS‐CoV‐2 using the ID NOW. Residual gargle samples were randomly selected among positive standard of care (SOC)‐nucleic acid amplification test (NAAT) samples. For testing on ID NOW, the manufacturer's instructions were followed, except for the specimen addition step: 500 µl of the gargle specimen was added to the blue sample receiver with a pipette and gently mixed. Among the 202 positive samples by SOC‐NAAT, 185 were positive by ID NOW (positive percent agreement [PPA]) = 91.6% (95% confidence interval [CI]: 86.9−95.0). For the 17 discordant samples, cycle threshold (C_t) values were all ≥31.0. The PPA was significantly lower among asymptomatic patients (84.4%; 95% CI: 73.2−92.3) versus symptomatic patients (95.2%; 95% CI: 89.8−98.2). The performance of the ID NOW for the detection of SARS‐CoV‐2 infection on gargle samples is excellent when C_t values are <31.0 and for patients that have COVID‐19 compatible symptoms.