Nasopharyngeal Testing among Healthcare Workers (HCWs) of a Large University Hospital in Milan, Italy during Two Epidemic Waves of COVID-19

Abstract

Background: since October 2020, a second SARS-CoV-2 epidemic wave has hit Italy. We investigate the frequency of positive nasopharyngeal swabs among HCWs during the two waves and the association with occupation and demographic characteristics. Methods: this is a retrospective, observational study conducted in a large university hospital in Milan, Northern Italy. We defined two epidemic waves: 1st (February 2020–July 2020) and 2nd (August 2020–January 2021). Occupational and demographic characteristics of HCWs who underwent nasopharyngeal swabs for SARS-CoV-2 were collected. Results: in the 1st wave, 242 positive subjects (7.2%) were found among 3378 HCWs, whereas in the 2nd wave, the positive subjects were 545 out of 4465 (12.2%). In both epidemic waves positive NPSs were more frequent among HCWs with health-related tasks and lower among students (p < 0.001). However, in the 2nd wave, workers engaged in non-health-related tasks had a peak of 20.7% positivity. Among 160 positive HCWs in the 1st wave who were tested again in the 2nd wave, the rate of reinfection based on SARS-CoV2 RNA cycle quantification value was 0.6%. Conclusions: during the 2nd epidemic wave, we confirmed a significant impact of COVID-19 among HCWs. The rise of infection rate among HCWs seems to reflect the increasing spread of SARS-CoV-2 among the overall population.

Comparison of Three Different Waves in Healthcare Workers during the COVID-19 Pandemic: A Retrospective Observational Study in an Italian University Hospital

“…We observed a significant impact of the COVID-19 pandemic among HCWs at the University Hospital of Bari during the second epidemic wave (63% of the total number of positive cases). A reasonable explanation is that the rise in the infection rate among HCWs seems to have reflected the increasing spread of SARS-CoV-2 among the overall population of the Puglia region in the same period, as evidenced by other recent studies on HCWs in Italy [ 29 ]. Moreover, during the 2nd wave, lockdown measures were less severe throughout the national territory, and there was a wider possibility of regional/national mobility than in the 1st wave.…”

Risk of reinfection and disease afterSARS‐CoV‐2 primary infection: Meta‐analysis

“…Of the 3282 papers initially retrieved, we included 91 cohort studies evaluating the onset of reinfection, severe and very severe/lethal COVID‐19 among 15,034,624 previously infected subjects (Figure 1), either among health care workers (27 publications; n = 37,598 2,8,9,15,17,24,36,38,42–59 ) or in the general population (67 publications; n = 14,997,026 3–7,10,12,16–23,25–27,43,49,60–106 ).…”

“…As shown in Table S1, most of the included studies ( n = 43) were carried out in Europe, 2,4–10,12,15,17,18,21,24,26,36,38,44,46–51,58,66,69,71,72,75,81,85–88,91–93,95,99,102 24 in the USA, 20,22,23,25,42,43,57,59,63,67,77,79,82–84,89,90,97,98,103,105–107 18 in Asia 3,16,19,27,45,52–54,56,60,62,64,65,70,73,74,100,101 and the remaining six in South America or South Africa 61,68,80,94,96,104 . The mean age of the participants ranged from 15 to 87 years, and the average follow‐up ranged from 29 to 371 days.…”

“…In the 59 available datasets, 2,3,5,6,10,16–22,25–27,36,44,46–59,63–67,69,71–74,79,82,84–87,90,93–95,99–104 a total of 1380 severe COVID‐19 diseases were diagnosed among 5,006,604 subjects with a previous infection, corresponding to a pooled rate of 0.02% (95% CI: 0.00%–0.04%—Table 1). This rate did not substantially vary when only the studies with longer time lag were considered, while it increased—still, however, remaining below 0.1%—when only the studies that used CDC criteria to define reinfections were included (summary rate 0.07%; 0.04%–0.10%).…”

“…The mean age of the participants ranged from 15 to 87 years, and the average follow‐up ranged from 29 to 371 days. Overall, 38 publications strictly followed the CDC criteria to identify the reinfections and were classified at low risk of misclassification bias 10,16,19,20,22–24,26,36,44,45,48–50,54,56,58,59,68,71,72,75,84,86,89–91,94,99,100,102 . All but five studies ( n = 3,854,961) 66,71,88,91,96 were completed before the emergence of BA.1/B.1.1.529 (Omicron) variant.…”