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.

During the recent pandemic, the fact that the clinical manifestation of COVID-19 may be indistinguishable from bacterial infection, as well as concerns of bacterial co-infection, have been associated with an increased use of antibiotics. The objective of this study was to assess the effect of targeted antibiotic stewardship programs (ASP) on the use of antibiotics in designated COVID-19 departments and to compare it to the antibiotic use in the equivalent departments in the same periods of 2018 and 2019. Antibiotic consumption was assessed as days of treatment (DOT) per 1000 patient days (PDs). The COVID-19 pandemic was divided into three periods (waves) according to the pandemic dynamics. The proportion of patients who received at least one antibiotic was significantly lower in COVID-19 departments compared to equivalent departments in 2018 and 2019 (Wave 2: 30.2% vs. 45.6% and 44.9%, respectively; Wave 3: 30.5% vs. 47.8% and 50.1%, respectively, p < 0.001). The DOT/1000PDs in every COVID-19 wave was lower than during similar periods in 2018 and 2019 (179-282 DOT/1000PDs vs. 452-470 DOT/1000PDs vs. 426-479 DOT/1000PDs, respectively). Moreover, antibiotic consumption decreased over time during the pandemic. In conclusion, a strong ASP is effective in restricting antibiotic consumption, particularly for COVID-19 which is a viral disease that may mimic bacterial sepsis but has a low rate of concurrent bacterial infection.

Myocarditis consists of an inflammation of the cardiac muscle, definitively diagnosed by endomyocardial biopsy. The causal agents are primarily infectious: in developed countries, viruses appear to be the main cause, whereas in developing countries rheumatic carditis, Chagas disease, and HIV are frequent causes. Furthermore, myocarditis can be indirectly induced by an infectious agent and occurs following a latency period during which antibodies are created. Typically, myocarditis observed in rheumatic fever related to group A streptococcal (GAS) infection occurs after 2- to 3-week period of latency. In other instances, myocarditis can occur within few days following a streptococcal infection; thus, it does not fit the criteria for rheumatic fever. Myocarditis classically presents as acute heart failure, and can also be manifested by tachyarrhythmia or chest pain. Likewise, GAS-related myocarditis reportedly mimics myocardial infarction (MI) with typical chest pain, electrocardiograph changes, and troponin elevation. Here we describe a case of recurrent myocarditis, 5 years apart, with clinical presentation imitating an acute MI in an otherwise healthy 37-year-old man. Both episodes occurred 3 days after GAS pharyngitis and resolved quickly following medical treatment.