Life expectancy in the United States fell by a year and a half in 2020 to 77.3 years, the lowest level since 2003, primarily due to the deaths caused by the COVID-19 pandemic, a U.S. health agency said on Wednesday.

It is the biggest one-year decline since World War Two, when life expectancy fell 2.9 years between 1942 and 1943, and is six months shorter than its February 2021 estimate, the U.S. Centers for Disease Control and Prevention (CDC) said.

“Life expectancy has been increasing gradually every year for the past several decades,” Elizabeth Arias, a CDC researcher who worked on the report, told Reuters. “The decline between 2019 and 2020 was so large that it took us back to the levels we were in 2003. Sort of like we lost a decade.”