Found a large study of adults in the United Kingdom and published by BMJ today.
They stress that causation cannot be inferred from this observational evidence, but say that vaccination “may contribute to reducing the health burden of the population due to the prolonged coronavirus, at least in the first few months after vaccination.”
Vaccines against COVID-19 are effective in reducing the rates of coronavirus infection, transmission, hospitalization, and death. Evidence also suggests that prolonged COVID decreases in infected individuals after vaccination, but the efficacy of vaccination on pre-existing long COVID is less clear.
The UK’s latest Office for National Statistics (ONS) survey showed 44% of people who reported prolonged COVID had symptoms for at least a year, two-thirds of whom reported symptoms severe enough to limit their daily activities.
So a team of researchers set out to estimate the association between the COVID-19 vaccine and prolonged COVID symptoms in adults with SARS-CoV-2 infection prior to vaccination.
They relied on ONS data for 28,356 adults aged 18 to 69 years (mean age 46; 56% women; 89% white) who received at least one dose of the COVID-19 vaccine after testing positive for SARS-CoV-2 infection.
They then tracked the presence of prolonged COVID symptoms over a seven-month follow-up period (February to September 2021).
Prolonged COVID symptoms of any severity were reported by 6,729 participants (24%) at least once during follow-up.
Before vaccination, the odds of being exposed to the coronavirus had long changed over time.
The first dose of the vaccine was associated with an initial 13% decrease in the odds of contracting COVID-19 for a long time, but it was not clear from the data whether this improvement lasted over the next 12 weeks, until a second dose of the vaccine was given.
Receiving a second dose of the vaccine was associated with an additional 9% reduction in the odds of contracting COVID-19 for a long time, and this improvement was maintained at least over an average follow-up of nine weeks.
Similar results were also found when a prolonged focus on COVID was severe enough to result in a limitation of daily activities.
Because of the observational study design, causation cannot be inferred, and the researchers cannot rule out the possibility that other, unmeasured factors, such as those related to a second dose of the vaccine, influenced their results.
However, the results were consistent after taking into account sociodemographic characteristics, health-related factors, type of vaccine, or duration from infection to vaccination, suggesting that they bear scrutiny.
As such, the researchers say: “Our results suggest that vaccinating previously infected persons may be associated with a reduced long-term COVID burden 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-term COVID, and studies “to understand the biological mechanisms that underlie any improvements in symptoms after vaccination, and that may contribute to the development of long-term COVID therapies.”
Are vaccines a potential treatment for COVID long term, ask researchers in a linked editorial?
They acknowledge that benefits are possible in some but not all individuals, and say the mechanisms underlying changes in COVID symptoms long after vaccination are still not fully understood.
Until a clear explanation is found, they say vaccination to reduce the risk of reinfection remains important for people with COVID for a long time, and the evidence so far suggests that the benefits are likely to outweigh any harms.
“Unfortunately, there are still many unknowns about the long-term prognosis of novel coronavirus, including the effect of booster vaccines or recurrent COVID-19,” they wrote, and call for further research “before we can hope to predict the effects of vaccination on individuals.” .”
The third dose of the COVID-19 mRNA vaccine appears to be safe
Prolonged course of COVID-19 disease symptoms after COVID-19 vaccination: a community cohort study, BMJ (2022). DOI: 10.1136 / bmj ‑ 2021‑069676
Submitted by the British Medical Journal
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