Breast density classification is largely determined by mammography, making the timing of the first screening mammogram clinically important.

This commentary suggests specific strategies and language that clinicians can use to address mistrust of COVID-19 vaccines among racial and ethnic minorities.

In this issue, Staub and colleagues provide a historical analysis of the response to the 1918–1919 influenza pandemic in Bern canton, Switzerland. The editorialist discusses their observations and highlights the dangers of eschewing the lessons that history provides.

Klompas and colleagues report an investigation of a SARS-CoV-2 cluster in an acute care hospital with transmission between patients and staff. The editorialists remind us of the need to reinforce and reeducate to improve practice of and adherence to important strategies that protect the entire health care ecosystem.

Public health interventions implemented during the coronavirus disease 2019 (COVID-19) pandemic are based on experience gained from past pandemics. The 1918 influenza pandemic is the most extensively researched historical influenza outbreak. All 9335 reports available in the State Archives on 121 152 cases of influenza-like illness from the canton of Bern from 473 of 497 municipalities (95.2%) were collected; the cases were registered between 30 June 1918 and 30 June 1919. The overall incidence rates of newly registered cases per week for the 9 greater regions of Bern for both the first and second waves of the pandemic were calculated. Relative incidence rate ratios (RIRRs) were calculated to estimate the change in the slope of incidence curves associated with public health interventions. During the first wave, school closures (RIRR, 0.16 [95% CI, 0.15 to 0.17]) and restrictions of mass gatherings (RIRR, 0.57 [CI, 0.54 to 0.61]) were associated with a deceleration of epidemic growth. During the second wave, in autumn 1918, cantonal authorities initially reacted hesitantly and delegated the responsibility to enact interventions to municipal authorities, which was associated with a lack of containment of the second wave. A premature relaxation of restrictions on mass gatherings was associated with a resurgence of the epidemic (RIRR, 1.18 [CI, 1.12 to 1.25]). Strikingly similar patterns were found in the management of the COVID-19 outbreak in Switzerland, with a considerably higher amplitude and prolonged duration of the second wave and much higher associated rates of hospitalization and mortality.

Immunization information systems (IISs) play a central role in coordinating distribution, administration, documentation, and monitoring of COVID-19 vaccination. In this commentary, the authors provide an introduction to IISs and discuss how clinicians can help maximize their utility in the COVID-19 pandemic.

The efficacy of rifaximin in the secondary prevention of overt hepatic encephalopathy (HE) is well documented, but its effectiveness in preventing a first episode in patients after transjugular intrahepatic portosystemic shunt (TIPS) has not been established.

Polack FP, Thomas SJ, Kitchin N, et al. Safety and efficacy of the BNT162b2 mRNA Covid-19 vaccine. N Engl J Med. 2020;383:2603-15. 33301246.

Lynch JB, Davitkov P, Anderson DJ, et al. Infectious Diseases Society of America guidelines on infection prevention for health care personnel caring for patients with suspected or known COVID-19. Clin Infect Dis. 2020. [Epub ahead of print.] 32716496.

Haimovich AD, Ravindra NG, Stoytchev S, et al. Development and validation of the quick COVID-19 Severity Index: a prognostic tool for early clinical decompensation. Ann Emerg Med. 2020;76:442-53. 33012378.

Dong YH, Chang CH, Wang JL, et al. Association of infections and use of fluoroquinolones with the risk of aortic aneurysm or aortic dissection. JAMA Intern Med. 2020;180:1587-95. 32897358.

Brouwer J, Nijenhuis VJ, Delewi R, et al. Aspirin with or without clopidogrel after transcatheter aortic-valve implantation. N Engl J Med. 2020;383:1447-57. 32865376.