The authors' full names, academic degrees, and affiliations are listed in the Appendix. Prof. Orkin can be contacted at c . m .

IMPORTANCE Administration of a BNT162b2 booster dose (Pfizer-BioNTech) to fully vaccinated individuals aged 60 years and older was significantly associated with lower risk of SARS-CoV-2 infection and severe illness. Data are lacking on the effectiveness of booster doses for younger individuals and health care workers.OBJECTIVE To estimate the association of a BNT162b2 booster dose with SARS-CoV-2 infections among health care workers who were previously vaccinated with a 2-dose series of BNT162b2. DESIGN, SETTING, AND PARTICIPANTSThis was a prospective cohort study conducted at a tertiary medical center in Tel Aviv, Israel. The study cohort included 1928 immunocompetent health care workers who were previously vaccinated with a 2-dose series of BNT162b2, and had enrolled between August 8 and 19, 2021, with final follow-up reported through September 20, 2021. Screening for SARS-CoV-2 infection was performed every 14 days. Anti-spike protein receptor binding domain IgG titers were determined at baseline and 1 month after enrollment. Cox regression with time-dependent analysis was used to estimate hazard ratios of SARS-CoV-2 infection between booster-immunized status and 2-dose vaccinated (booster-nonimmunized) status.EXPOSURES Vaccination with a booster dose of BNT162b2 vaccine. MAIN OUTCOMES AND MEASURESThe primary outcome was SARS-CoV-2 infection, as confirmed by reverse transcriptase-polymerase chain reaction. RESULTS Among 1928 participants, the median age was 44 years (IQR, 36-52 years) and 1381 were women (71.6%). Participants completed the 2-dose vaccination series a median of 210 days (IQR, 205-213 days) before study enrollment. A total of 1650 participants (85.6%) received the booster dose. During a median follow-up of 39 days (IQR, 35-41 days), SARS-CoV-2 infection occurred in 44 participants (incidence rate, 60.2 per 100 000 person-days); 31 (70.5%) were symptomatic. Five SARS-CoV-2 infections occurred in booster-immunized participants and 39 in booster-nonimmunized participants (incidence rate, 12.8 vs 116 per 100 000 person-days, respectively). In a time-dependent Cox regression analysis, the adjusted hazard ratio of SARS-CoV-2 infection for booster-immunized vs booster-nonimmunized participants was 0.07 (95% CI, 0.02-0.20).CONCLUSIONS AND RELEVANCE Among health care workers at a single center in Israel who were previously vaccinated with a 2-dose series of BNT162b2, administration of a booster dose compared with not receiving one was associated with a significantly lower rate of SARS-CoV-2 infection over a median of 39 days of follow-up. Ongoing surveillance is required to assess durability of the findings.

In our cohort of 70 MSM patients with monkeypox, more than one third presented with proctitis. In two-thirds of proctitis patients, there was no typical rash upon presentation, and in one-fifth, there was no rash at all, making the diagnosis a challenge. A rectal swab for monkeypox PCR can be diagnostic.

The current monkeypox virus global spread and lack of data regarding clinical specimens’ infectivity call for examining virus infectivity, and whether this correlates with results from PCR, the available diagnostic tool. We show strong correlation between viral DNA amount in clinical specimens and virus infectivity toward BSC-1 cell line. Moreover, we define a PCR threshold value (Cq ≥ 35, ≤ 4,300 DNA copies/mL), corresponding to negative viral cultures, which may assist risk-assessment and decision-making regarding protective-measures and guidelines for patients with monkeypox.

This study demonstrated good short-term safety profile after a third dose of BNT162b2 vaccine among HCWs. There were more frequent local reactions and less systemic reactions compared to the second dose. HCW's who reported reactions had higher pre-booster titer of anti-S1 antibodies compared to those reported no reactions.

Background The COVID-19 pandemic poses many epidemiological challenges. The investigation of nosocomial transmission is usually performed via thorough investigation of an index case and subsequent contact tracing. Notably, this approach has a subjective component and there is accumulating evidence that whole genome sequencing of the virus may provide a more objective insight. Methods We report a large nosocomial outbreak in one of the medicine departments in our institution. Following intensive epidemiological investigation, we discovered that one of the patients involved was suffering from persistent COVID-19 while initially thought to be a recovering patient. She was therefore deemed to be the most likely source of the outbreak. We then performed whole genome sequencing of the virus of fourteen infected individuals involved in the outbreak. Results Surprisingly, the results of whole genome sequencing refuted our initial hypothesis. A phylogenetic tree of the samples showed multiple introductions of the virus into the ward, one of which led to a cluster of ten of the infected individuals. Importantly, the results pointed in the direction of a specific index patient that was different from the one that arose from our initial investigation. Conclusions These results underscore the important added value of using whole genome sequencing in epidemiological investigations as it may reveal unexpected connections between cases and aid in understanding transmission dynamics, especially in the setting of a pandemic where multiple possible index cases exist simultaneously.

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Background Nocardia cyriacigeorgica was first described in 2001. It is an emerging pathogen that mainly affects immunocompromised patients. A brain abscess caused by N. cyriacigeorgica has been reported only in immunocompromised hosts. We present a rare case of brain abscess caused by N. cyriacigeorgica in an adult male receiving low dose steroids. Case presentation A 75-year-old male weekend gardener without an immunocompromising condition presented with neurological complaints that were initially attributed to an ischemic stroke. Due to the unusual presentation and rapid progression, his condition was thought to be caused by a cerebral space-occupying lesion. He underwent an emergent right-sided parietal craniotomy and the histopathological report of the specimen was an abscess caused by N. cyriacigeorgica. The patient received appropriate antibiotic treatment and completely recovered without sequelae. Conclusions Nocardia species are a rare cause of brain abscess in immunocompetent patients. Their clinical presentation can mimic other more common cerebral diseases, such as brain tumors (primary and secondary) and stroke. The possibility of an abscess caused by N. cyriacigeorgica should also be considered in the differential diagnosis in an immunocompetent patient.