Reduced Mortality During Holidays and the COVID-19 Pandemic in Israel

Evidence suggests varied trends in mortality surrounding the holiday period. Most studies support an association between increased mortality rates and holidays. We compare the effect of the number of holiday days per week on the overall mortality rate in the Israeli population. Between 2000-2020, we see significantly reduced mortality rates in weeks containing national holidays. We observed the same trend in all-cause mortality during the 3-weeks COVID-19 pandemic lockdown. As the Israeli health care system, and hospitals especially, function near peak capacity year-round, we propose that reduced medical service utilization during holidays and the COVID-19 lockdown period might underlie the lower mortality rates.

Performing risk stratification for COVID-19 when individual level data is not available, the experience of a large healthcare organization

With the global coronavirus disease 2019 (COVID-19) pandemic, there is an urgent need for risk stratification tools to support prevention and treatment decisions. The Centers for Disease Control and Prevention (CDC) listed several criteria that define high-risk individuals, but multivariable prediction models may allow for a more accurate and granular risk evaluation. In the early days of the pandemic, when individual level data required for training prediction models was not available, a large healthcare organization developed a prediction model for supporting its COVID-19 policy using a hybrid strategy. The model was constructed on a baseline predictor to rank patients according to their risk for severe respiratory infection or sepsis (trained using over one-million patient records) and was then post-processed to calibrate the predictions to reported COVID-19 case fatality rates. Since its deployment in mid-March, this predictor was integrated into many decision-processes in the organization that involved allocating limited resources. With the accumulation of enough COVID-19 patients, the predictor was validated for its accuracy in predicting COVID-19 mortality among all COVID-19 cases in the organization (3,176, 3.1% death rate). The predictor was found to have good discrimination, with an area under the receiver-operating characteristics curve of 0.942. Calibration was also good, with a marked improvement compared to the calibration of the baseline model when evaluated for the COVID-19 mortality outcome. While the CDC criteria identify 41% of the population as high-risk with a resulting sensitivity of 97%, a 5% absolute risk cutoff by the model tags only 14% to be at high-risk while still achieving a sensitivity of 90%. To summarize, we found that even in the midst of a pandemic, shrouded in epidemiologic "fog of war" and with no individual level data, it was possible to provide a useful predictor with good discrimination and calibration.