One in 20 people still have Covid-19 symptoms a year after infection, according to the largest UK study looking at the “lasting impacts” of the virus.
The analysis by Imperial College London involved 276,000 members of the public who were regularly tested for the coronavirus during the pandemic as part of the React surveillance study.
In total, 59 per cent of these participants tested positive for the virus between 2020 and last year, and were asked to report their symptoms and any long-term effects.
Although most people recovered from Covid-19 within two weeks, one in 13 reported symptoms three months later, meeting the threshold for “long Covid”.
One in 20 patients had symptoms a year after infection, with mild fatigue, difficulty concentrating and joint pain the most common.
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Other persistent symptoms included loss or change of sense of smell or taste, shortness of breath, severe fatigue, chest tightness or pain and poor memory.
The authors of the study, published in the journal Nature Communications, said it provided a “snapshot of the continued impact of Covid-19 in the UK”.
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They said that for most people the virus was “short-lived” and that symptoms lasted ten days on average — but others went on to develop “persistent and burdensome illness”.
Women, patients with other health conditions and those with severe initial infections were more likely to develop long-term symptoms.
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The analysis also found that the likelihood of getting long Covid symptoms was decreasing as immunity built up in the population, making infections less severe.
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Professor Paul Elliott, director of the React programme, said: “We find that the variant people are infected with, the initial severity of their symptoms and whether they have pre-existing health conditions all have an impact on whether they will develop lasting symptoms.”
The study found that people infected in the Omicron wave of the pandemic — from December 2021 onwards — were 88 per cent less likely to develop persistent symptoms than those infected with early “wild-type” strains of the virus.
Dr Christina Atchison, lead author, said: “While the landscape has changed considerably since the early peak of the Covid-19 pandemic, this analysis shows that a proportion of adults are still experiencing lasting symptoms.
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“Importantly, we find that compared to wild-type virus, those infected when Omicron was dominant were far less likely to report symptoms lasting beyond 12 weeks. This may reflect the changing levels of immunity in the population from previous exposure to the virus and vaccination.”
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About two million people reported suffering from long Covid symptoms last year. The NHS has set up 90 specialist clinics in England to help people recover.
Scientists remain unsure about what causes long Covid, and think the underlying cause may vary depending on patients’ response to the initial infection.
In some patients, Covid may send their immune systems into overdrive, meaning they attack not just the virus but their own organs, causing lasting damage. The virus can also damage blood vessels, contributing to heart problems.
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There is also evidence it causes “micro-clotting” in blood, reducing the amount of oxygen pumped around the body.
The React study, which was commissioned by the government during the pandemic, will continue to carry out analysis on the long-term impact of Covid.
Helen Ward, professor of public health at Imperial College London, said: “The study has shown some big variation in people’s symptoms post-Covid. While we have gained valuable insights into the groups at risk of lasting symptoms, we are undertaking detailed interviews to further understand the variation in people’s experiences and the impact on their everyday lives.
“We are also planning further follow-up of people involved in the React studies to assess the broader longer-term impact of the pandemic on health and well-being.”
