Factors Associated with SARS-CoV-2 Infection before Vaccination among European Health Care Workers

Main Article Content

Ihab Mansour
Alessandro Godono
Emanuele Sansone
Giovanni Visci
Gianluca Spiteri
Maria Grazia Lourdes Monaco
Dana Mates
Agripina Rascu
Xavier Duval
Enrico Pira
Catalina Ciocan
Francesco Violante
Vittorio Lodi
Giuseppe De Palma
Emma Sala
Marco Dell'Olmo
Corrado Negro
Loretta Casolari
Masha Abedini
Giorgia Ditano
Shuffield Asafo
Paolo Boffetta
Orchestra Wp5 Working Group


COVID-19, determinants, HCWs, meta-analyses, multicentric, FFP2, mask


Background: Health care workers (HCWs) were on the frontline of the current pandemic. We aimed at identifying determinants of SARS-CoV-2 infection and the effectiveness of personal protection equipment (PPE) worn by HCWs before vaccination. Methods: We abstracted data on SARS-CoV-2 infection based on positive PCR results and sociodemographic characteristics of 38,793 HCWs from public hospitals and public health authorities from 10 European centers. We fitted cohort-specific multivariate logistic regression models to identify determinants of infection and combined the results using random-effects meta-analyses. Results: The overall prevalence of infection before vaccination among HCWs was 9.58%. Infection was associated with the presence of selected symptoms; no association was found between sociodemographic factors and increased risk of infection. The use of PPE and particularly FFP2/FFP3 masks had a different protective effect during the first and second waves of the COVID pandemic. Conclusions: The study provides evidence that mask use was the most effective PPE in preventing SARS-CoV-2 infection among HCWs.

Abstract 274 | PDF Downloads 284


1. Iversen K, Bundgaard H, Hasselbalch RB, et al. Risk of COVID-19 in health-care workers in Denmark: an obser-vational cohort study. Lancet Infect Dis. 2020;20(12):1401-1408. Doi: 10.1016/S1473-3099(20)30589-2
2. Montecucco A, Dini G, Rahmani A, et al. Investigating SARS-CoV-2 transmission among co-workers in a Universi-ty of Northern Italy during COVID-19 pandemic: an observational study. Med Lav. 2021;112(6):429-435. Published 2021 Dec 23. Doi: 10.23749/mdl.v112i6.12527
3. Collatuzzo G, Mansour I, Ciocan C, et al. Effectiveness of prevention of SARS-CoV-2 transmission among unvac-cinated Italian healthcare workers. Med Lav. 2022;113(6):e2022050. Published 2022 Dec 7. Doi: 10.23749/mdl.v113i6.13577
4. Violante T, Violante FS. Surgical masks vs respirators for the protection against coronavirus infection: state of the art. Med Lav. 2020;111(5):365-71.
5. Ciocan C, Clari M, Fabbro D, et al. Impact of wearing a surgical mask on respiratory function in view of a wide-spread use during COVID-19 outbreak. A case-series study. Med Lav. 2020;111(5):354-364. Published 2020 Oct 31. Doi: 10.23749/mdl.v111i5.9766
6. CDC, Centers for disease control and prevention. 2020. Using Personal Protective Equipment (PPE). Available online at: https://www.cdc.gov/coronavirus/2019-ncov/hcp/using-ppe.html [Last accessed 07-03-2023].
7. Gordon C, Thompson A. Use of personal protective equipment during the COVID-19 pandemic. Br J Nurs. 2020;29(13):748-752. Doi: 10.12968/bjon.2020.29.13.748
8. Chia SE, Koh D, Fones C, et al. Appropriate use of personal protective equipment among healthcare workers in public sector hospitals and primary healthcare polyclinics during the SARS outbreak in Singapore. Occup Envi-ron Med. 2005;62(7):473-7. Doi: 10.1136/oem.2004.015024
9. Phan LT, Maita D, Mortiz DC, et al. Personal protective equipment doffing practices of healthcare workers. J Oc-cup Environ Hyg. 2019;16(8):575-581. Doi: 10.1080/15459624.2019.1628350
10. Chung H, He S, Nasreen S, et al. Effectiveness of BNT162b2 and mRNA-1273 covid-19 vaccines against symp-tomatic SARS-CoV-2 infection and severe COVID-19 outcomes in Ontario, Canada: Test negative design study. The BMJ. 2021;374:n1943. Doi: 10.1136/bmj.n1943
11. Sansone E, Sala E, Tiraboschi M, et al. Effectiveness of bnt162b2 vaccine against sars-cov-2 among healthcare workers. Med Lav. 2021;112(3):250-255. Doi: 10.23749/mdl.v112i3.11747
12. Bergwerk M, Gonen T, Lustig Y, et al. Covid-19 Breakthrough Infections in Vaccinated Health Care Workers. N Eng J Med. 2021;385(16):1630-1631. Doi: 10.1056/nejmoa2109072
13. Chemaitelly H, Tang P, Hasan MR, et al. Waning of BNT162b2 Vaccine Protection against SARS-CoV-2 Infection in Qatar. N Eng J Med. 2021;385(24):e83. Doi: 10.1056/nejmoa2114114
14. Abu-Raddad LJ, Chemaitelly H, Bertollini R. Effectiveness of mRNA-1273 and BNT162b2 Vaccines in Qatar. N Eng J Med. 2022;386(8):799-800. Doi: 10.1056/nejmc2117933
15. Victoria Hall, Sarah Foulkes, Ferdinando Insalata, Peter Kirwan. Protection against SARS-CoV-2 after Covid-19 Vaccination and Previous Infection. N Eng J Med. 2022;386:1207-1220. Doi: 10.1056/NEJMoa2118691
16. Nick Andrews, Elise Tessier, Julia Stowe, Charlotte Gower. Duration of Protection against Mild and Severe Dis-ease by Covid-19 Vaccines. N Eng J Med. 2022;386:340-350. Doi: 10.1056/NEJMoa2115481
17. Hacisuleyman E, Hale C, Saito Y, et al. Vaccine Breakthrough Infections with SARS-CoV-2 Variants. N Eng J Med 2021;384(23):2212-2218. Doi: 10.1056/nejmoa2105000
18. Lewis D. Why the WHO took two years to say COVID is airborne. Nature. 2022;604:26.
19. Boffetta P, Violante F, Durando P, et al. Determinants of SARS-CoV-2 infection in Italian healthcare workers: a multicenter study. Sci Rep. 2021;11(1):5788. Doi: 10.1038/s41598-021-85215-4
20. Folgueira MD, Munoz-Ruiperez C, Alonso-Lopez MA, Delgado R. SARS-CoV-2 infection in Health Care Workers in a large public hospital in Madrid, Spain, during March 2020. medRxiv. 2020;(March). Doi: https://doi.org/10.1101/2020.04.07.20055723
21. Barek MA, Aziz MA, Islam MS. Impact of age, sex, comorbidities and clinical symptoms on the severity of COVID-19 cases: A meta-analysis with 55 studies and 10014 cases. Heliyon. 2020;6(12):e05684. Doi: 10.1016/j.heliyon.2020.e05684
22. Peckham H, de Gruijter NM, Raine C, et al. Male sex identified by global COVID-19 meta-analysis as a risk factor for death and ITU admission. Nat Commun. 2020;11(1):6317. Published 2020 Dec 9. Doi: 10.1038/s41467-020-19741-6
23. Scozzari G, Costa C, Migliore E, et al. Prevalence, persistence, and factors associated with sars-cov-2 igg seroposi-tivity in a large cohort of healthcare workers in a tertiary care university hospital in northern Italy. Viruses. 2021;13(6):1064. Doi: 10.3390/v13061064
24. Barrett ES, Horton DB, Roy J, et al. Prevalence of SARS-CoV-2 infection in previously undiagnosed health care workers in New Jersey, at the onset of the U.S. COVID-19 pandemic. BMC Infect Dis. 2020;20(1):853. Doi: 10.1186/s12879-020-05587-2
25. Garzaro G, Clari M, Ciocan C, et al. COVID-19 infection and diffusion among the healthcare workforce in a large university-hospital in Northwest Italy. Med Lav. 2020;111(3):184-194. Doi: 10.23749/mdl.v111i3.9767
26. Eyre DW, Lumley SF, O’donnell D, et al. Differential occupational risks to healthcare workers from SARS-CoV-2 observed during a prospective observational study. eLife. 2020;9:e60675. Doi: 10.7554/ELIFE.60675
27. UK Health Security Agency. SARS-CoV-2 variants of concern and variants under investigation in England. 2021. Available online at: https://www.gov.uk/government/publications/investigation-of-sars-cov-2-variants-technical-briefings [Last accessed 07-03-2023].
28. Sandri MT, Azzolini E, Torri V, et al. SARS-CoV-2 serology in 4000 health care and administrative staff across seven sites in Lombardy, Italy. Sci Rep. 2021;11(1):12312. Doi: 10.1038/s41598-021-91773-4
29. Rader B, White LF, Burns MR, et al. Mask-wearing and control of SARS-CoV-2 transmission in the USA: a cross-sectional study. Lancet Digit Health. 2021;3(3)e148-e157. Doi: 10.1016/S2589-7500(20)30293-4
30. Talic S, Shah S, Wild H, et al. Effectiveness of public health measures in reducing the incidence of covid-19, SARS-CoV-2 transmission, and covid-19 mortality: Systematic review and meta-analysis. The BMJ. 2021;375:e068302. Doi: 10.1136/bmj-2021-068302
31. Gandhi M, Rutherford GW. Facial Masking for Covid-19 – Potential for “Variolation” as We Await a Vaccine. N Engl J Med. 2020;383(18):e101. Doi: 10.1056/NEJMp2026913
32. Levine Z, Earn DJD. Face masking and COVID-19: potential effects of variolation on transmission dynamics. J R Soc Interface. 2022;19(190):20210781. Doi: 10.1098/rsif.2021.0781
33. Riediker M, Briceno-Ayala L, Ichihara G, et al. Higher viral load and infectivity increase risk of aerosol transmis-sion for Delta and Omicron variants of SARS-CoV-2. Swiss Med Wkly. 2022;152:w30133. Published 2022 Jan 6. Doi: 10.4414/smw.2022.w30133
34. European Center for Disease Prevention and Control. SARS-COV-2 Delta variant now dominant in much of the European Region and efforts must be reinforced to prevent transmission, warn WHO/Europe and ECDC. 2021. Available online at: https://www.ecdc.europa.eu/en/news-events/sars-cov-2-delta-variant-now-dominant-european-region [Last accessed 07-03-2023].
35. European Center for Disease Prevention and Control. Clinical characteristics of COVID-19. 2022. Available online at: https://www.ecdc.europa.eu/en/covid-19/latest-evidence/clinical [Last accessed 07-03-2023].
36. Gómez-Ochoa SA, Franco OH, Rojas LZ, et al. COVID-19 in Health-Care Workers: A Living Systematic Review and Meta-Analysis of Prevalence, Risk Factors, Clinical Characteristics, and Outcomes. Am J Epidemiol. 2021;190(1):161-175. Doi: 10.1093/aje/kwaa191