COVID-19 Case Mortality Rates Continue to Decline in Florida

We studied COVID-19 case mortality in Florida among four successive cohorts of persons at least 50 years of age, each of whom we followed for 28 to 48 days from date of diagnosis. The cohorts were separated by date of diagnosis into four nonoverlapping intervals: March 29 - April 18; April 29 - May 19; May 21 - June 10; and June 14 - July 4, 2020. Case mortality rates declined consistently and significantly over the course of the four intervals: 57% among those aged 50-59 years; 62% among those aged 60-69 years; 52% among those aged 70-79 years; and 34% among those aged 80 or more years. These findings were consistent with progressive improvements in the medical care of COVID-19 patients. We further studied case mortality by hospitalization status. The case mortality rate among hospitalized patients aged 60-69 years fell significantly from the first to the third interval. During the fourth interval, an apparent rise in mortality among hospitalized patients in the same age group was mirrored by a significant decline in mortality among those not hospitalized. These findings were consistent with the out-of-hospital treatment of some patients who would have previously been hospitalized. This study relies exclusively on publicly available, aggregate health data that contain no individual identifiers. The author has no competing interests and no funding sources to declare. This article represents to the sole opinion of its author and does not necessarily represent the opinions of the Massachusetts Institute of Technology, the National Bureau of Economic Research, Eisner Health, or any other organization.