PEOPLE who are vaccinated following a Covid infection appear less likely to experience Long Covid, according to new research.

The study, carried out by the Office for National Statistics (ONS), is the latest to explore whether the vaccines could be used as a potential treatment to alleviate symptoms such as fatigue, muscle pain, and brain fog which can debilitate some patients for months after infection.

The study, published in the BMJ, tracked over 28,000 people aged 18 to 69 across the UK who had received at least one vaccine dose after previously testing positive for the virus.

Of these, 6729 participants self-reported experiencing Long Covid symptoms of any severity during the study period from February to September 2021, and 4747 said the symptoms limited their daily activities.

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Long Covid was defined as symptoms such as headaches, insomnia, muscle ache, loss of taste, memory problems, and difficulty concentrating which had persisted at least 12 weeks from infection.

Researchers found that the odds of participants experiencing Long Covid symptoms decreased by 13% immediately following a first dose vaccination, with a further reduction of 9% following a second dose, although they stressed that the data is observational and does not prove that vaccination relieved the symptoms.

Scientists in an accompanying editorial noted that the study lacked an control arm of unvaccinated participants to evaluate natural recovery rates as a comparison.

However, the ONS researchers said their results were consistent after taking account of sociodemographic characteristics, health related factors, vaccine type, or duration from infection to vaccination, suggesting that they withstand scrutiny.

They write: “Our results suggest that vaccination of people previously infected may be associated with a reduction in the burden of Long Covid on population health, at least in the first few months after vaccination.”

They call for further research into the long-term relationship between vaccination and Long Covid, and studies “to understand the biological mechanisms underpinning any improvements in symptoms after vaccination, which may contribute to the development of therapeutics for Long Covid”.

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One hypothesis is that vaccination helps to eliminate viral reservoirs in the body by increasing antibody levels, but it remains unclear whether residual virus is the root cause of Long Covid.

Covid vaccines are effective at reducing rates of coronavirus infection, hospital admission, and death.

Existing research also indicates that people who are vaccinated prior to their first Covid exposure roughly halve their risk of developing Long Covid.

However, the effect of vaccines on people who already have Long Covid is described as “a contentious area for both patients and healthcare professionals”.

The latest survey by the ONS shows that 44% of people who report Long Covid have had symptoms for at least one year, two thirds of whom report symptoms severe enough to limit their day-to-day activities.

A previous French study, not yet peer-reviewed, suggested that Long Covid sufferers who subsequently received a vaccine were twice as likely to experience a complete resolution of symptoms compared to those who remained unvaccinated.

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However, another small study led by Japanese researchers found that 61% of people experienced no change in their condition in the two weeks after vaccination, while 21% reported a worsening of Long Covid symptoms and only 16% had an improvement.

The ONS Long Covid study is the largest of its kind to date, however.

The researchers said the evidence “so far suggests that benefits are likely to outweigh any harms”, including by reducing the risk of reinfection, but added: “Unfortunately, many unknowns remain about the long term prognosis of Long Covid, including the effect of booster vaccines or recurrent Covid-19.”