Hengameh Goodarzi (Berlin / DE), Elke Lemke (Berlin / DE), Solvy Wolke (Berlin / DE), Frank Schwab (Berlin / DE), Beate Schlosser (Berlin / DE), Marco Paul (Berlin / DE), Annika Brodzinski (Berlin / DE), Giovanni-Battista Fucini (Berlin / DE), Britta Kohlmorgen (Berlin / DE), Sandra Jendrossek (Berlin / DE), Seven Aghdassi (Berlin / DE), Brar Piening (Berlin / DE), Christine Geffers (Berlin / DE), Miriam Wiese-Posselt (Berlin / DE), Luisa Denkel (Berlin / DE)
Introduction: Despite the widespread deployment of SARS-CoV-2 vaccines, breakthrough infections continue to pose challenges, particularly in healthcare settings. Nosocomial outbreaks remain a significant concern, warranting an in-depth investigation into the risk factors associated with SARS-CoV-2 acquisition among vaccinated individuals.
Goals: To identify risk factors for SARS-CoV-2 acquisition among vaccinated patients and healthcare providers in nosocomial outbreaks at Charité hospitals in Berlin, Germany, in 2022.
Materials & Methods: In this retrospective case-control study, we investigated SARS-CoV-2 acquisition in 114 nosocomial SARS-CoV-2 outbreaks notified to the healthcare authorities in 2022. Cases included 587 patients and 385 staff members who tested positive for SARS-CoV-2 during the outbreaks. Controls (not tested positive for SARS-CoV-2), were matched (1:1) to cases based on their patient/staff status and the time shared with a case on the ward 14 days before the case tested positive. All participants were fully vaccinated and completed a questionnaire regarding potential risk or protective factors for SARS-CoV-2 acquisition. Univariable analysis and multivariable logistic regression models were used.
Results: In total, 271 cases and 271 controls participated in the study. Our findings indicate that cases were more likely to be immunized > 3 months ago compared with controls (77.5% versus 68.6%, p= 0.02). Cases more often suffered from diabetes (15.2% versus 9.0%, p = 0.03) and less often had a previous SARS-CoV-2 infection (6.7 versus 15.7%, p < 0.01). Multivariable logistic models identified previous SARS-CoV-2 infection as an independent protective factor (OR=0.25, 95% CI: 0.11- 0.53). Independent risk factors were immunization > 3 months ago (OR=1.6, 95% CI: 1.05 – 2.7) and diabetes (OR =2.26, 95% CI: 1.13 – 4.72).
Summary: Our analyses suggest that certain primary diseases and an immunization older than 3 months were associated with increased risks of breakthrough infections in healthcare settings. However, a previous SARS-CoV-2 infection may have a protective effect. These findings represent preliminary results and warrant further validation.