April 8 (UPI) -- The number of hospitalized COVID-19 patients in the United States who died from the disease declined by nearly 50% as the pandemic progressed and new ways for managing care emerged, a study published Thursday by JAMA Network Open found.
At the start of the pandemic, in March 2020, about 11% of patients hospitalized following infection died -- a figure that rose to nearly 20% in April before dropping to just over 9% in November, the data showed.
Even though the percentage of young adults ages 18 to 49 hospitalized with the virus increased to just under 30% from 20% over the same period, the influx of younger, presumably healthier patients was not a factor in the decline in death rates linked with the disease, researchers said.
"Reductions in mortality rates did not appear to be associated with the age distribution of hospitalized patients with [COVID-19]-positive tests," researchers from Kenilworth, N.J.-based pharmaceutical company Merck wrote.
The changes "were likely because of new therapies and improvements in the clinical management of patients with [COVID-19] infection," they said.
The United States is averaging just over 60,000 new COVID-19 cases per day, and nearly 5,000 of these cases per day, on average, are admitted to a hospital for treatment, according to the Centers for Disease Control and Prevention.
For this study, the Merck researchers analyzed data on more than 500,000 people treated at 209 hospitals across the country between March and November of last year.
Just under 10% of the patients included in the study tested positive for COVID-19. Of those with positive tests, about half were male and over age 65, while 27% were age 50 to 64 and 25% were age 18 to 49.
Nearly 12% of the patients who tested positive for the virus died in the hospital, 1% of whom were under age 18 and 21% of whom were older than 75.
The largest declines in virus-related death rates over the nine-month period were seen in patients age 75 and older, to 17% from 36%, and in those ages 65 to 75, to 10% from 23%.
Although "the U.S. was largely unprepared for COVID-19 [initially], we definitely learned methods for treating patients with severe ... symptoms over time," public health expert Brandon Brown, who was not part of this study, told UPI.
"This likely accounted for the decrease in hospital mortality," said Brown, an associate professor of social medicine population and public health at the University of California-Riverside.