Background: Despite a vaccination rate of 82.0% (n = 123/150), a SARS-CoV-2 (Alpha) outbreak with 64.7% (n = 97/150) confirmed infections occurred in a nursing home in Bavaria, Germany. Objective: the aim of this retrospective cohort study was to examine the effects of the Corminaty vaccine in a real-life outbreak situation and to obtain insights into the antibody response to both vaccination and breakthrough infection. Methods: the antibody status of 106 fully vaccinated individuals (54/106 breakthrough infections) and epidemiological data on all 150 residents and facility staff were evaluated. Results: SARS-CoV-2 infections (positive RT-qPCR) were detected in 56.9% (n = 70/123) of fully vaccinated, compared to 100% (n = 27/27) of incompletely or non-vaccinated individuals. The proportion of hospitalized and deceased was 4.1% (n = 5/123) among fully vaccinated and therewith lower compared to 18.5% (n = 5/27) hospitalized and 11.1% (n = 3/27) deceased among incompletely or non-vaccinated. Ct values were significantly lower in incompletely or non-vaccinated (p = 0.02). Neutralizing antibodies were detected in 99.1% (n = 105/106) of serum samples with significantly higher values (p < 0.001) being measured post-breakthrough infection. $\alpha$-N-antibodies were detected in 37.7% of PCR positive but not in PCR negative individuals. Conclusion: Altogether, our data indicate that SARS-CoV-2 vaccination does provide protection against infection, severe disease progression and death with regards to the Alpha variant. Nonetheless, it also shows that infection and transmission are possible despite full vaccination. It further indicates that breakthrough infections can significantly enhance $\alpha$-S- and neutralizing antibody responses, indicating a possible benefit from booster vaccinations.

Diagnosis of Lyme borreliosis (LB) is mainly based on clinical symptoms, patient's history, and serological testing. Despite a lack of standardization, polymerase chain reaction (PCR) has gained importance for the detection of Borrelia DNA. So far, extensive studies comparing different protocols used in molecular diagnostic or research setting are missing. Here, we describe a European-wide comparison of commercial and in-house PCR protocols using a standardized DNA panel including all relevant Borrelia burgdorferi sensu lato (Bbsl) species to explore variation in PCR results in different laboratories. A DNA testing panel composed of 90 DNA samples from 14 Bbsl strains in six different dilutions, plus six specificity controls, was sent blinded to 34 laboratories (33 European plus one in the US). The results from a total of 57 different amplification protocols were collected and compared regarding their detection limits, specificity, and sensitivity over all Bbsl strains for each dilution included in the DNA panel. While the detection limits showed vast differences (>10⁵ genome equivalents (GE)) between different amplification protocols, none of the most commonly used PCR targets (ospA, 16S rRNA, flagellin, 5S-23S intergenic spacer) significantly outperformed other PCR targets. Interestingly, large differences in detection limits were found not only between different protocols, but also when the same protocol was used on different Bbsl species (>10⁵ GE) and even on different strains of the same Bbsl species (>10⁴ GE). Specificity also varied between different protocols, with many protocols recognizing relapsing fever Borreliae. A standardization of PCR methods used for confirmation of LB diagnosis is urgently needed.