October 17, 2022 12:18 PM EDT

COVID-19 has caused an inordinate number of deaths around the world so far, causing life-expectancies to plunge. Historically, countries have recovered from other so-called “mortality shocks,” such as the 1918 flu and two world wars, within one to two years. But the shock of the pandemic is enduring in many places.

A study published Oct. 17 in Nature Human Behavior reviewed life-expectancy trends in 29 countries during 2021, building on previous data the scientists had analyzed from 2020, and found that COVID-19 continued to account for most life-expectancy losses in 2021. But those life-expectancy losses from the pandemic are dissipating in some countries with relatively high rates of vaccination and infection-derived immunity, which both contribute to lower COVID-19 deaths. Four countries in western Europe—Belgium, France, Switzerland, and Sweden—have fully restored their population’s life expectancy back to pre-pandemic levels, and four others have nearly done so, while other countries did not experience additional losses in 2020 compared to 2021. But the U.S. and 11 countries, including many in eastern Europe, continue to record excess mortality.

“We found it was indeed possible for nations to recover from drastic and historic life-expectancy losses,” says Jonas Scholey, research scientist at the Max Planck Institute for demographic research and co-author of the paper. “But within our sample, it was not the norm.”

The reasons for disparities among the countries, not surprisingly, has to do with how resilient their health-care systems are at bouncing back from the burden of caring for COVID-19 patients. It also relates to the countries’ underlying health trends that had been in place before the pandemic.

Since COVID-19 hit people ages 60 and older particularly hard, the countries that recovered best were those that lowered excess mortality among this population most quickly, through successful vaccination campaigns and the capacity to provide antiviral treatments and intensive care. Belgium, which showed the most impressive recovery out of any country studied, was particularly strong in these areas; for people 60 and older, life-expectancy rates dropped about a year in 2020 but went up by about 10 months in 2021, nearly returning to 2019 levels.

The U.S. also improved mortality rates among the elderly in 2021, but those gains were offset by increases in deaths among younger populations, including from gun violence and opioid overdoses. On top of deaths caused by COVID-19, deaths related to other chronic conditions, such as obesity and Type 2 diabetes, also continued to increase, keeping mortality among working-age populations high. Overall, life expectancy in the U.S. dropped by more than two years during the pandemic compared to 2019 levels.

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In eastern Europe, persistent losses in life expectancy are likely due to fractured health-care systems that still have not recovered from the overwhelming impact of the pandemic, says Scholey. “I’m not at all optimistic about how fast health-care systems can regenerate from the shock they had to absorb over the past 2.5 years,” he says. “By that I mean people in the health care system as well; some have resigned and others suffer from burnout, and this has an effect on what health systems can do.” Many countries in eastern Europe showed deeper life-expectancy losses in 2021 than in 2020; the populations of Bulgaria and Slovakia, for example, both lost about two years in 2021 due to COVID-19, which is higher than the 18-month and 9-month deficits they recorded, respectively, in 2020.

It’s still too early to determine how big an impact the pandemic will have on life-expectancy long term. It’s also impossible at this point to assess the impact of delayed health care for conditions like cancer and heart disease, which may have an eventual effect on mortality. Experts expect the consequences of people skipping or not getting treatments because of COVID-19 to emerge in mortality and life-expectancy trends in the next few years.

Still, with more of the world’s population now vaccinated, it’s possible that in the coming year, some of the life-expectancy losses in countries could begin to reverse, says Scholey. “I am cautiously optimistic that the excess deaths this winter [from COVID-19] won’t be as pronounced in many countries as they have been over the last two years. But with a virus as unpredictable as SARS-CoV-2, “we’ll have to see.”

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