Symptoms of long COVID include fatigue, brain fog, muscle pain, shortness of breath, and loss of taste and smell.
In the largest survey to date of vaccinated people with long COVID, 57% of respondents reported an overall improvement in their symptoms following vaccination, while 19% reported an overall deterioration.
Respondents who received the Moderna vaccine were more likely to report improvements and potentially less likely to report deterioration, compared with those who received other vaccines.
Possible explanations for improvements after vaccination include clearing the residual virus and restoring a healthy balance to the immune system.
The Office for National Statistics in the United Kingdom estimates that 13.7% of people who test positive for COVID-19 still experience symptoms 4 months later.
There is no proven treatment for long COVID, but anecdotal reports have begun to emerge of people recovering after COVID-19 vaccination.
At the same time, some people with the condition have been reluctant to get vaccinated because of concerns that it will make their symptoms worse.
A small study, which has yet to be published in a peer-reviewed journal, found that the AstraZeneca and Pfizer-BioNTech vaccines were associated with overall improvements in symptoms. There was no evidence of declines in quality of life or mental well-being.
Researchers in the United Kingdom have now conducted the largest survey to date of changes in 14 long COVID symptoms following vaccination. The study has yet to be published in a peer-reviewed journal.
There were 900 respondents, most of whom had received the AstraZeneca, Pfizer-BioNTech, or Moderna vaccines.
More than 70% reported they experienced symptoms for 9 months or more.
Combining the results across all the symptoms, 56.7% of respondents experienced an improvement, 18.7% experienced a deterioration, and 24.6% remained unchanged.
Respondents who received the Moderna vaccine, which is an mRNA vaccine, were most likely to report improvements and least likely to report a deterioration of their symptoms.
Scientists at the University of Exeter and the University of Kent in the United Kingdom collaborated with the patient advocacy group LongCovidSOS on the survey.
“The results of this survey should reassure people with long COVID that their chance of experiencing an overall worsening of their symptoms after vaccination is small. More than half saw at least some improvement to their symptom status.”
The authors call for clinical trials to investigate further the possible benefits of vaccination for people with long COVID.
LongCovidSOS posted the survey on its website and social media accounts and sent it to people on its mailing list.
In addition to asking respondents to assess the overall change in their condition, the survey invited them to rate each symptom on a scale of 1 to 10 before the first dose and after each dose of the vaccine.
The survey advised respondents to allow at least a week to pass before completing the survey, to allow any of the normal side effects of vaccination to subside.
The time between vaccination and completion of the survey ranged from zero to 127 days, with around 40% having had the shot more than 30 days previously.
In 41% of respondents, COVID-19 was confirmed with a PCR or antibody test.
The most frequently reported symptoms before vaccination were fatigue, brain fog, muscle pain, shortness of breath, and chest pain or palpitations.
The Moderna vaccine appeared to have the most positive impact on all 14 symptoms surveyed.However, it is worth noting that this was only after the first dose, so the findings do not tell us how the three vaccines would perform after both doses. This is something that would need further investigation.
Among respondents who reported any improvement in their symptoms, almost half said it had been sustained, although for 20% of these individuals, they were less than 10 days post-vaccination.
Chris Coleman, Ph.D., assistant professor of infection immunology at the University of Nottingham in the United Kingdom, told Medical News Today that the simplest explanation was that vaccination cleared lingering virus particles from patients’ bodies.
“[T]he vaccine could, in theory, ‘tip the balance’ in favor of recovery and clear the virus — either because the initial immune response was weak or deficient in some other way,” said Prof. Coleman, who was not involved in the survey.
However, he pointed out that acute viral infections usually last only a few days or weeks, with any further symptoms caused by disruptions in immune responses.
In that case, he said, the vaccine may dampen down these responses.
“Of course, it could be a placebo effect, as some of those symptoms are a bit difficult to quantify,” he added.
David Strain, M.D., from the University of Exeter in the United Kingdom, who helped organize the survey and analyze the results, acknowledged that a placebo effect was one possible explanation for the findings.
However, he said the prevailing expectation before the survey was that vaccination would make symptoms worse rather than better.
Alternatively, some of the patients may have recovered anyway over time, without vaccination.
Dr. Strain told MNT that the results of the survey should be interpreted with caution and will need to be confirmed in a prospective study.
“The key aim was to determine whether there would be an excess risk to people with long COVID from vaccination,” he said. “We believe this survey [provides] the reassurance that many needed to go ahead and get their vaccine.”
The researchers acknowledge some other limitations of the survey.
For example, because participants were recruited via social media and online long COVID support groups, they may not represent the wider population of people with long COVID.
In total, 90.8% of respondents identified as white and around 80% were female, which are much higher proportions than in the wider population of people who have had COVID-19 in the United Kingdom.
In addition, the survey relied on respondents’ recollections of changes in their symptoms that may have occurred several weeks previously.
Finally, COVID-19 was not confirmed in around 60% of respondents. Most of the infections occurred during the first wave of the pandemic when few had the chance to be tested.
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