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October 30, 2020 -- A new study conducted by researchers at Imperial College London found the COVID-19 infection fatality ratio is about 1.15% of infected people in high-income nations and 0.23% in low-income nations..

The infection fatality ratio (IFR) represents the proportion of deaths among all infected individuals. It is “a key statistic for estimating the burden of COVID-19 and has been continuously debated throughout the current pandemic,” the Imperial College London said in a news release.

Researchers screened 175 studies and identified 10 antibody surveys to obtain estimates of the infection fatality ratio, the news release said.

The new study confirms that the coronavirus is deadlier for older people, with the risk of death doubling for every eight years of aging and ranging from 0.1% for people under 40 and 5% among people over 80 years old. The disparity between high and low-income nations is due largely to facts that high-income nations tend to have larger number of elderly in their populations whereas low-income nations’ population tend to skew youngers.

“Although the elderly are by far at the highest risk of dying due to COVID-19, the risk in middle age is still high,” said co-author Dr. Lucy Okell.For example, we estimate that around 1 in 260 people aged 50-55 years die if infected. We calculated COVID-19 fatality largely based on the first wave of the epidemic in a number of countries and we hope and expect to see some reduction in fatality now due to new clinical knowledge and treatment, but this remains a dangerous virus.”

"The study did not find a large effect of possible waning of antibodies on our IFR estimates at the times the serosurveys were done, but it will become increasingly important to account for potential declines in antibody levels to avoid overestimating the IFR in future," the news release said.

“We know that antibody tests are not perfect, and there may be a considerable number of people who do not mount a detectable antibody response to SARS-CoV-2,” said Dr. Robert Verity, a study co-author.

However, even when this uncertainty is taken into account, we still find that COVID-19 has a high fatality rate - on the order of 1% for a typical high-income country. This risk is concentrated in older ages, with the probability of dying from COVID-19 doubling approximately every eight years.

Higher-income countries are seeing higher fatality rates largely because those countries typically have longer expected life spans. High-income nations tend to have a more elderly population whereas low-income nations tend to skew younger, and old age is a key driver of COVID deaths.

The study doesn’t compare the deadliness of the coronavirus to seasonal influenza. The World Health Organization has estimated seasonal flu has a mortality rate of about 0.1%. That’s about10 times less than the infection fatality ratio that Imperial College of London scientists found for coronavirus in high-income nations.

The WHO cautioned that access to and the quality of health care is also a major factor in flu mortality.

Correction: This story incorrectly said researchers did not take into account previous studies of how long antibodies last. 

Show Sources

Imperial College of London. "Report 34 - COVID-19 Infection Fatality Ratio Estimates from Seroprevalence." "COVID-19 deaths: Infection fatality ratio is about 1% says new report."

World Health Organization. "Coronavirus disease (COVID-19): Similarities and differences with influenza."

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