Background and Methods: Vaccination is currently considered the most successful strategy for combating the SARS-CoV-2 virus. According to short-term clinical trials, protection against infection is estimated to reach up to 95% after complete vaccination (≥14 days after receipt of all recommended COVID-19 vaccine doses). Nevertheless, infections despite vaccination, so-called breakthrough infections, are documented. Even though they are more likely to have a milder or even asymptomatic course, the assessment of further transmission is highly relevant for successful containment. Therefore, we calculated the real-world transmission risk from fully vaccinated patients (vaccination group, VG) to their close contacts (CP) compared with the risk from unvaccinated reference persons matched according to age, sex, and virus type (control group = CG) utilizing data from Cologne’s health department. Results: A total of 357 breakthrough infections occurred among Cologne residents between 27 December 2020 (the date of the first vaccination in Cologne) and 6 August 2021. Of the 979 CPs in VG, 99 (10.1%) became infected. In CG, 303 of 802 CPs (37.8%) became infected. Factors promoting transmission included non-vaccinated status (β = 0.237; p < 0.001), male sex (β = 0.079; p = 0.049), the presence of symptoms (β = −0.125; p = 0.005), and lower cycle threshold value (β = −0.125; p = 0.032). This model explained 14.0% of the variance (corr. R²). Conclusion: The number of transmissions from unvaccinated controls was three times higher than from fully vaccinated patients. These real-world data underscore the importance of vaccination in enabling the relaxation of stringent and restrictive general pandemic control measures.

Vancomycin-resistant enterococci (VRE) are important nosocomial pathogens that require effective infection control measures, representing a challenge for healthcare systems. This study aimed at identifying risk factors associated with prolonged VRE carriage and determining the rate of clearance that allows the discontinuation of contact precautions. During a 2-year study, screening was performed in patients with a history of VRE or at risk of becoming colonized. After bacterial identification and antibiotic susceptibility testing, glycopeptide resistance was confirmed by PCR. Isolates were compared via whole genome sequence-based typing. Risk factors were recorded, and follow-up screening was performed upon readmission, defining patients as long-term carriers if still colonized ≥10 weeks after first detection. Of 1059 patients positive for VRE, carriage status was assessed upon readmission in 463 patients. VRE was cleared in 56.4% of the cases. Risk factors associated with long-term persistence were hospital stays (frequency, length), hemato-oncological disease, systemic treatment with steroids, and use of antibiotics. No specific genotypic clustering was observed in patients with VRE clearance or persistence. VRE clearance is possibly underestimated. The identification of risk factors favoring long-term carriage may contribute to a targeted implementation of infection control measures upon readmission of patients with history of VRE.

With high numbers of refugees arriving in Europe uncertainty exists as to whether multidrug-resistant organisms are imported into the healthcare system. In our study, we identified 383 refugee-inpatients admitted to the University Hospital Münster, Germany between September 2015 and September 2016. For this patient cohort screening for Methicillin-resistant Staphylococcus aureus (MRSA), multidrug-resistant Gram-negative bacteria (MDR-GNB) and Vancomycin-resistant enterococci (VRE) was recommended in our institution. Until May 2016 pre-emptive isolation was applied to all refugee-inpatients until the exclusion of these multidrug-resistant organisms. MRSA were found in 34 refugee-patients (9.8%), MDR-GNB in 25 refugee-patients (12.9%) and VRE in none of the refugee patients. We did not find any strains carrying carbapenemases. Whole genome sequencing (WGS) data demonstrated that the respective isolates were genetically heterogeneous and revealed no transmission of refugee-patient isolates to other patients. We therefore omitted pre-emptive isolation as an infection control measure for this group of patients. Furthermore, molecular typing did not show evidence for nosocomial transmission from refugee-patients to other patients. Standard hygiene measures successfully prevented the transmission of refugee-patient isolates to other patients and as a result introduction into the healthcare system. This underlines that any multidrug-resistant organisms present within this cohort are not of any extraordinary concern for health systems.

Purpose To determine the prevalence of multidrug resistant (MDR) bacteria in a cohort of pregnant refugee women. Methods In a prospective case control study, surveillance cultures for MDR bacteria (methicillin-resistant Staphylococcus aureus [MRSA], vancomycin-resistant enterococci [VRE], MDR Gram-negative bacteria [MRGN]) were analysed between October 2015 and June 2016 from a cohort of 50 pregnant refugee women and 50 resident controls in the obstetric unit of a German tertiary referral hospital. Results Prevalence of MRSA was noticeably higher among refugee women compared to residents (6 vs. 0%). In addition, a trend towards a higher prevalence of VRE and MDR Gram-negative bacteria in refugees was shown (1.8 vs. 0%). Conclusions Due to the higher prevalence of MDR bacteria, surveillance cultures are justified in order to prevent nosocomial spread of MDR bacteria.

Background: SARS-CoV-2 has been spreading worldwide since late 2019. Before vaccines became available, exclusively non-pharmaceutical measures were used to prevent transmission of infection. Despite the fact that vaccinations are now available, it is still important to identify relevant transmission routes in order to contain the COVID-19- or further pandemics. Therefore, this study aims to systematically analyse data from the largest public health department in Germany to determine the significance of the various known and unknown transmission situations in terms of the proportion of infections. Methods: All infections in Cologne were systematically recorded by the local health department. In addition to clinical data, the transmission situations were recorded and categorised as pertaining to social contact, work contact, travellers, health care workers, users of educational institutions, visitors of community institutions, infection in the context of medical treatment, and unknown infection. Findings: The analysis included 25,966 persons. A transmission situation could be identified in 82.7% of the cases (n = 21,477). Most persons (42.1%) were infected due to social contact, primarily within their own household. Another 22.3% were infected at their place of work; this was particularly common among staff members of medical facilities, nursing homes and educational institutions. In 17.3% of the cases, the transmission situation remained unknown; the cases with unknown transmission situation were slightly more often symptomatic (75.2%) than the cases with known transmission situation (69.4%). Interpretation: Considering that during the study period the leading strains were the wild-type and alpha-variant transmission rather occurred during scenarios involving close contacts than in anonymous situations. Presumably, however, the findings can be transferred to the new variants. Therefore, in order to prevent transmission, besides vaccination regular antigen tests and/or appropriate protective measures remain relevant until this pandemic has subsided.

Since its first description in November 2021, the SARS-CoV-2 variant of concern Omicron (B.1.1.529) has emerged as the dominant strain in the COVID-19 pandemic. To date, it remains unclear if boosted vaccination protects against transmission. Using data from the largest German Public Health Department, Cologne, we analyzed breakthrough infections in booster-vaccinated infected persons (IP; booster-vaccinated group (BVG); n = 202) and fully vaccinated, not boosted SARS-COV2-positive patients (>3 month after receiving the second dose; unboosted, fully vaccinated group (FVG); n = 202) to close contacts compared to an age- and sex-matched unvaccinated control group (UCG; n = 202). On average, IPs had 0.42 ± 0.52 infected contacts in relation to the total number of contacts in the BVG vs. 0.57 ± 0.44 in the FVG vs. 0.56 ± 0.43 in the UVG (p = 0.054). In the median test, pairwise comparison revealed a significant difference between the BVG and both other groups; no difference was found between the fully vaccinated and the unvaccinated control group. Now, these findings must be verified in larger samples, considering the role of Omicron subvariants and the vaccination status of the contact person. However, the importance of the booster vaccination in breaking possible chains of infection in the immune escape variant Omicron is obvious.