INDIANAPOLIS -- Using the results of the first U.S. statewide random sample study of SARS-CoV-2 prevalence, researchers were able to calculate the first generalizable infection fatality rate (IFR) for COVID-19 by age, race, ethnicity and sex.
Because many COVID-19 deaths occur among residents of nursing homes, this study was the first to determine the probability of death from the SARS-CoV-2 infection among people not living in institutions like nursing homes or prisons.
The study found that age, more than race or sex, determines how deadly the virus is. People over 60 years of age had an IFR almost 2%, or 1 death for every 50 people who get infected. This IFR is approximately 2.5 times deadlier than seasonal flu for the same population.
“Hoosiers who are 60 and older are facing a higher possibility of death if they contract COVID-19,” said Justin Blackburn, lead author and associate professor at the IU Richard M. Fairbanks School of Public Health. “While the overall IFR is relatively low in other age groups, the long-term outcomes are not yet known. Furthermore, infected individuals who are asymptomatic can unknowingly transmit the virus to someone at increased risk.”
To determine the IFR, the researchers combined prevalence estimates from the first phase of the statewide random sample study with confirmed COVID-19 deaths in Indiana. When testing concluded on April 29, 2020, Indiana had recorded 1099 COVID-19 deaths, however 495 of those deaths occurred in non-institutionalized populations.
Nursing home residents represented 54.9% of Indiana’s deaths at this date.
Using the non-institutionalized population, researchers determined the overall IFR for Indiana to be 0.26%.
The IFR for Hoosiers who are 12 to 40 years old is 0.01% (children under 12 were not included in the study). That rate increases to 0.12% for those who are 40 to 59 years old.
“These are the first precise estimates that allow us to determine the increased risk of death among people over 60 years old,” said Nir Menachemi, senior author on the study and professor and Fairbanks Endowed Chair in the Fairbanks School of Public Health. “Previous studies determined the fatality rate based on case counts which are known to undercount infections. We looked at other factors such as race, ethnicity and sex, but the greatest predictor of death is age.”
The researchers also found that the IFR for non-Whites is more than three times that for Whites, despite the COVID-19 deaths for non-Whites being 5.6 years younger on average.
“Based on our research, we believe we have one of the most accurate and generalizable COVID-19 infection fatality rates in the U.S. Deaths can be prevented by reducing the number of people who get infected, and social distancing, wearing a mask and avoiding crowded spaces is known to help reduce infections,” said Menachemi.
The full article is available in Annals of Internal Medicine.
Blackburn J, Yiannoutsos CT, Carroll AE, Halverson PK, Menachemi N. Infection Fatality Ratios for COVID-19 Among Noninstitutionalized Persons 12 and Older: Results of a Random-Sample Prevalence Study [published online ahead of print, 2020 Sep 2]. Ann Intern Med. 2020;10.7326/M20-5352. doi:10.7326/M20-5352