COVID-19 hospital outbreaks: Protecting healthcare workers to protect frail patients. An Italian observational cohort study

Abstract

Objectives: To determine the prevalence of SARS-CoV-2 infection among exposed healthcare workers (HCWs) after preventive protocol implementation.

Methods: A total of 5750 HCWs were included in the study. Those in contact with COVID-19 patients were allocated into a high-risk or a low-risk group based on contact type (PPE- or non-PPE-protected); high-risk workers underwent nasopharyngeal swab tests, while among low-risk workers, swab tests were carried out only for symptomatic workers (active surveillance). The prevalence was determined by real-time reverse transcriptase-polymerase chain reaction on nasopharyngeal samples.

Results: 3570 HCWs had contact with 1065 COVID-19 patients. Among them, 3494 were subjected to active surveillance (low-risk group); 2886 (82.60%) were subjected to a swab test; and 15 were positive (0.52%). Seventy-six HCWs (2.13% of exposed) were included in the high-risk group, and a swab test was mandatory for each participant. Overall, 66 (86.84% of high-risk) were negative, and 10 were positive (13.16%), resulting in a higher risk of infection than in the low-risk group [OR = 29.00; 95% CI:12.56-66.94; p < 0.0001].

Conclusion: To date, the SARS-CoV-2 infection prevalence is 0.70% among exposed HCWs and 0.435% among all HCWs working at the examined university hospital. The correct use of PPE and the early identification of symptomatic workers are essential factors to avoiding nosocomial clusters.

Keywords: COVID-19; Healthcare workers; Prevention protocol.

Figure 1

Preventive protocol flowchart. The flowchart extensively describes the preventive protocol initiated in the cohort of 5750 workers. Between March 11 and April 29, 3570 HCWs (62.09% of the total) had contact with 1065 COVID-19 patients. Based on preventive officers’ reports, 3494 HCWs, having PPE-protected close contacts (97.87%), were subjected to active surveillance (Low-risk Group). Among them, 2886 (82.60%) manifested at least one evocative symptom (described in Table 2) and were subjected to a swab test; 2871 (99.48% of low-risk symptomatic HCWs) were negative, and only 15 HCWs (0.53%) were positive, of whom 2 were positive after the second test. On the other hand, 76 HCWs were included in the high-risk group due to non-PPE-protected contacts, and a swab test was mandatory for each participant. Overall, 66 HCWs (86.84% of the high-risk group) were negative, and 10 were positive (13.16%), of whom 2 had a statistically higher risk of infection after the second test than the low-risk group [OR = 29.00; CI95%:12.56–66.94; p < 0.0001]. In yellow boxes, checkpoints are performed by prevention officers.

Figure 2

Nasopharyngeal and oropharyngeal swab tests. Data from 3109 nasopharyngeal and oropharyngeal swab tests performed in the cohort of 2962 HCWs. As shown in Figure 3, the weekly incidence of positive tests slowly decreased after protocol initiation, from 4.3% in week 2 (March 19–March 25) to 0.47% in week 7 (April 23–April 29).

Figure 3

Incidence of positive swab tests. Weekly incidence of positive swab tests in the worker cohort.