Pre-vaccine COVID-19: US study reveals hospitalization rate of 5.7% and fatality rate of 1.7%

By Tarun Sai LomteReviewed by Susha Cheriyedath, M.Sc.May 17 2024

In a recent study published in the journal Emerging Infectious Diseases, researchers estimated hospitalization and mortality rates in people infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the United States (US) in the pre-vaccination period.

The coronavirus disease 2019 (COVID-19) pandemic caused more than 20 million cases, 480,000 hospitalizations, and 350,000 deaths in the US until December 2020. COVID-19 case detection was considerably affected by commercial testing and at-home diagnostic tests beginning in mid-December 2020.

Further, the development of vaccines after mid-December 2020 has substantially reduced hospitalization and mortality rates. Studies have reported higher case fatality rates associated with specific individual-level, country-level, and clinical characteristics. Moreover, precise hospitalization and mortality estimates in SARS-CoV-2-naïve populations are limited.

Study: Estimates of SARS-CoV-2 Hospitalization and Fatality Rates in the Prevaccination Period, United States. Image Credit: Photo Spirit / Shutterstock

About the study

In the present study, researchers estimated COVID-19 hospitalization and mortality rates before vaccines were available in the US. The Centers for Disease Control and Prevention (CDC) received COVID-19 case reports from epidemiologists from 56 US jurisdictions (50 states, the District of Columbia, the US Virgin Islands, Puerto Rico, Guam, Northern Mariana Islands, and New York City).

Datasets of hospitalization and mortality were generated for jurisdictions with more than 80% of cases having non-missing CDC hospitalization and death queries for illnesses between May 1 and December 1, 2020. The team estimated COVID-19 case hospitalization and fatality rates by age group, sex, race/ethnicity, hospitalization, intensive care unit (ICU) admission, and symptom status. Demographic characteristics of cases were described.

Findings

Overall, more than 10.33 million COVID-19 cases were reported to the CDC during the study period. Of these, 58.8% and 63.5% had valid, non-missing data on hospitalization and death, respectively. Accordingly, hospitalization and death datasets included over 2.47 million and 4.7 million cases from 21 and 22 jurisdictions, respectively.

Upper and lower estimates of case-hospitalization (gray) and case-fatality (black) rates by age group of patients with SARS-CoV-2 infection, United States, 2020.  For case-hospitalization, lower bound was calculated by including cases with unknown hospitalization information as not hospitalized and upper bound by excluding cases with unknown hospitalization information. For case-fatality, lower bound was calculated by including cases with unknown death status as alive and upper bound by excluding cases with unknown death status information. Reports in which no response was provided about death or hospitalization were excluded from the respective rate calculation. Inset graph provides greater detail for younger age groups by using smaller y-axis values.

The resultant study populations closely matched the 2019 US Census population distribution by age group and sex, albeit were variable by race/ethnicity. The overall COVID-19 case hospitalization rate was 5.7%. It was < 8.3% in all age groups up to 64 years, viz., 5% in infants (< 1 year), 1.2% in those aged 1–4, and 0.6% in the 5–14 age group.

The hospitalization rate increased steadily in individuals aged 15 or older. It was 16.3% in those aged 65–74 and 25.9% in 75–84 and > 85 age groups. The hospitalization rate was 5.2% in females and 6.2% in males. Females had lower rates in all age groups except those aged 15–34. Further, the hospitalization rate was 3.3% among asymptomatic cases and 6.3% among symptomatic individuals.

In addition, non-Hispanic African American or Black individuals had the highest hospitalization rate (11.4%). Consistently, it was the highest in non-Hispanic African American or Black individuals (14%) after adjusting for age, followed by those who were Asian or Pacific Islander (11%). Non-Hispanic White people showed the lowest hospitalization rate (6.8%).

The case fatality rate was 1.7% overall. It was below 1.6% in people aged up to 64 years, with 0.05% in infants, 0.01% in 1–4 and 5–14 age groups, 4.7% in people aged 65–74, 12% in the 75–84 age group, and 23.6% in those aged 85 or older. The fatality rate was 1.5% in females and 1.9% in males. Lower fatality rates were observed in all age groups except infants in females.

The fatality rate was the same (1.7%) in asymptomatic and symptomatic subjects. It was the highest in people who were Asian or Pacific Islander (3%), followed by non-Hispanic African American or Black individuals (2.7%). All racial/ethnic groups except non-Hispanic whites had higher fatality rates after adjusting for age. The fatality rates in non-hospitalized, hospitalized, and ICU patients were 0.6%, 17.6%, and 44.2%, respectively.

Conclusions

In sum, the study presented COVID-19 case hospitalization and fatality rates before vaccination or at-home testing was available in the US. Age was the primary driver of hospitalization and mortality. Rates exhibited a U-shaped curve, i.e., lower in infants (under one year), lowest in children aged 5–14, and highest among adults over 65. Overall, the findings underscore the severity of infections early in the pandemic and suggest that appropriate measures in historically underserved racial/ethnic groups and high-risk groups will be paramount.