For the first time since the start of the pandemic, the number of people dying in the U.K. with a recent positive Covid-19 test is significantly overstating the true death toll from the virus, according to new data.
In recent weeks, a commonly watched measure of Covid-19 mortality—deaths within 28 days of a positive test—has been around 30% higher than the number of registered deaths involving Covid-19 and nearly 75% higher than the number of registered deaths where Covid-19 was named as the main cause.
That gap contrasts with most of the pandemic, when those two metrics tracked one another closely—at least after the first wave, when a lack of testing capacity meant that the death certificate figures significantly exceeded deaths within 28 days of a positive test.
The pandemic has exacted an enormous death toll in the U.K. and around the world. But the latest figures offer hope that now more people in the U.K. are dying with Covid-19, not because of it. Whether that will translate to other countries, such as the U.S., remains to be seen.
The U.S. hasn’t shown a significant divergence between front-line mortality data and the death certificate counts that accrue more slowly, but eventually provide what the Centers for Disease Control and Prevention says is the most accurate tally. The two systems seem to track closely so far, according to Robert Anderson, chief of the mortality statistics branch at the CDC’s National Center for Health Statistics.
The agency has counted close to 900,000 Covid-19 deaths via death certificates, at least 90% of which record Covid-19 as the underlying cause. The remaining deaths list it as a contributing cause, according to the CDC. Epidemiologists believe this U.S. count likely misses many Covid-19 deaths, especially from early 2020, when tests were in short supply.
The U.K. data provide another indication of how the Omicron variant—more transmissible but often less serious than its predecessors—is changing the shape of the pandemic. With hospitalizations and deaths falling, the U.K. government said this week it will lift all remaining Covid-19 restrictions in England on Feb. 24, including the legal requirement to isolate for five days after testing positive, if the downward trends continue.
Although case numbers reached record highs last month, hospitalizations and deaths have been well below the levels during the winter peak a year ago. High infection numbers mean many people dying from other causes happen to also have the virus.
Scientists are using automation, real-time analysis and pooling data from around the world to rapidly identify and understand new coronavirus variants before the next one spreads widely. Photo Illustration: Sharon Shi
Soon after the pandemic began, the U.K. government started tracking deaths within 28 days of a positive test to get a near real-time snapshot of those dying from the new disease. Collecting data on the number of death certificates which mention Covid-19 as a contributing cause is more precise, but takes longer to collate.
The two sets of data overlap substantially but not completely. Some Covid-19 fatalities aren’t immediately captured in the death-certificate data due to delays in registrations. But that proportion is likely to be small: Deaths are typically registered within five days—as required by law unless a coroner’s investigation is needed—and nearly 90% are registered within two weeks, according to the U.K.’s Office for National Statistics.
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The snapshot figure has the potential to overcount and undercount true Covid-19 deaths. It misses people who die more than a month after testing positive for the virus, perhaps because they spent many weeks in intensive care. But it also includes people who died of other causes soon after testing positive for the virus.
During most of the pandemic, the snapshot figures closely tracked the measure using death certificates and at times even undershot it. But now they appear to be diverging, as sky-high infection rates from Omicron mean that many people dying from other causes happen to also have the virus.
Death-certificate data from England and Wales show that, in the five weeks from Dec. 25 to Jan. 28, Covid-19 was implicated in 5,755 deaths, and was the underlying cause in 4,304 of those. That compares to 7,480 deaths within 28 days of a positive test recorded over the same period, a number which includes people who had Covid-19 when they died but for whom the virus played no part in their death.
“We didn’t see this before Omicron,” said Paul Hunter, Professor in Medicine at the University of East Anglia. “It’s because Omicron is causing a lot of infections, and is much less likely to kill you.”
The Covid-19 memorial wall in London.
The data, from the U.K.’s Office for National Statistics, also show that deaths from any cause are lower than the five-year average, based on the years 2016 to 2019, and 2021. The ONS excluded 2020 from the average to prevent the pandemic from having an outsize impact on average death figures. That means that, despite high levels of Covid-19 infection, fewer deaths from any cause are occurring than would be expected at this time of year. Earlier waves of the pandemic were associated with surges in so-called excess deaths.
High levels of immunity in the U.K. from vaccination and prior infection, more treatments to forestall serious illness, and the milder symptoms associated with the Omicron variant have kept a lid on the worst effects of the virus, despite record-high case numbers. More than 37 million people in the U.K. have received a booster, around two-thirds of all people aged 12 and over. Among those aged 70 and older—the group most at risk of severe illness—more than 90% have received a booster shot.
The snapshot measure of deaths within 28 days of a positive Covid-19 test may soon become less relevant, but while cases are high it is still a useful early indicator, according to Prof. Hunter. Although higher than death-certificate data, they show a similar falling trend.
Another aspect of the death-certificate data suggests that the virus is becoming less deadly. In the week ending Jan. 28, doctors listed Covid-19 as an underlying cause in 986 deaths. That is 71% of all deaths where the disease contributed to the death, much lower than the 90% figure during the peak of the Alpha wave last winter. While any mention of Covid-19 means that the virus was thought to play some role in the death, that role appears to be shrinking.
—Jon Kamp contributed to this article.
Write to Denise Roland at Denise.Roland@wsj.com
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