COVID-19 was the third-leading cause of death in the U.S. between March 2020 and October 2021, according to an analysis of federal data released Tuesday.

Researchers at the National Cancer Institute, part of the National Institutes of Health, analyzed death certificate data and found that the coronavirus accounted for 350,000 deaths — 1 in every 8 — in the U.S. during that 20-month period.

The data illustrates the toll of the pandemic, as COVID-19 was a top-five cause of death in every age group aged 15 years and older. 

Heart disease was the No. 1 cause of death, followed by cancer, which accounted for a total of 1.29 million deaths combined.

Compared with 2020, deaths from COVID-19 in 2021 decreased in ranking among those aged 85 years and older but increased in ranking among those aged 15 to 54 years and became the leading cause of death among those aged 45 to 54 years.

Among those aged 85 and older, the coronavirus was the second-leading cause of death in 2020 but dropped to third in 2021, likely because of targeted vaccination efforts in this age group. 

According to the study, COVID-19 increased from the fifth- to the second-leading cause of death among people aged 35 to 44 years, from 6,100 deaths up to 13,000.

Compared with 2020, COVID-19 became the fourth-leading cause of death in 2021 among those aged 25 to 34 years, at 5,000 deaths, and those aged 15 to 24 years, with 1,100 deaths.

The authors noted that the increased ranking of COVID-19 as a leading cause of death in some age groups matches a downward age shift in the distribution of COVID-19 deaths in the U.S. in 2021 compared with 2020. This trend could be attributed to higher vaccination rates among elderly and more vulnerable people. 

Vaccines are now authorized for every American at least 6 months old, but only about 67 percent of the population is up to date with the shots. Booster shots are authorized and recommended for everyone down to age 5, but less than 50 percent of the eligible population has received one.