A large British study in BMJ suggests that vaccination against COVID-19 after infection reduces the risk of persistent symptoms, with an initial drop of 12.8% after the first dose and an 8.8% drop after the second, although the effects at long term are unclear.
Published this week, the observational study included 28,356 participants aged 18 to 69 in the Office for National Statistics COVID-19 Infection Survey who had received one or more doses of the AstraZeneca/Oxford adenoviral vector or Pfizer mRNA vaccines /BioNTech or Moderna after Infection by covid19.
The team, led by researchers from the Office for National Statistics, monitored participants from February 3 to September 5, 2021, to identify people with COVID-19 infections and symptoms for at least 12 weeks. The study period spanned the emergence and dominance of the SARS-CoV-2 Delta variant but predated the emergence of Omicron.
Participants answered survey questions and took a COVID-19 polymerase chain reaction (PCR) test once a week for 1 month, then once a month for a year or more, and those in households in which a household contact had tested positive for COVID-19 were asked to provide monthly blood samples for SARS-CoV-2 antibody testing.
The average age of participants was 46, 55.6% were female and 88.7% were white. Follow-up averaged 141 days after the first dose of COVID-19 vaccine for all participants and 67 days after the second dose for the 83.8% who received both doses.
Lower risks of COVID long after first dose
Of the 28,356 participants, 23.7% reported prolonged COVID symptoms of any severity one or more times during follow-up. One dose of vaccine was linked to an initial 12.8% reduction in the likelihood of long COVID, followed by increases and decreases (0.3% per week; 95% confidence interval [CI]-0.6% to 1.2%).
A second dose of vaccine was linked to an initial reduction of 8.8% (95% CI, -14.1% to -3.1%) in the risk of persistent symptoms, decreasing by 0.8% per week (CI at 95%, -1.2% to -0.4%) after. Results did not differ by sociodemographic factors, health status, hospital admission for initial infection, type of vaccine, or time between diagnosis and vaccination.
Of all participants, 16.7% said that long COVID symptoms limited their ability to participate in activities at least once during follow-up. A first dose of vaccine was linked to an initial 12.3% (95% CI, -19.5% to -4.5%) reduction in the risk of long activity-limiting COVID effects (0.9% per week; 95% CI, -0.2% to 1.9%) until receipt of a second dose. A second dose was linked to an initial 9.1% (95% CI, -15.6% to -2.1%) decrease in the likelihood of long activity-limiting COVID, followed by a reduction 0.5% per week (95% CI, -1.0% to 0.05%) until last follow-up.
The risk of long COVID after a first dose of COVID-19 vaccine decreased over time from infection, at 24.8%, 16.5%, and 4.8% for participants who received their first dose 9, 12 and 15 months after diagnosis.
The likelihood of experiencing most symptoms, as well as more than three or five symptoms at once, decreased after each vaccination, with the greatest reductions in loss of smell (−12.5%), loss of taste (−9.2%) and sleep disorders (−8.8%). After the second dose, the largest decreases occurred in fatigue (−9.7%), headache (−9.0%), and sleep disturbance (−9.0%).
The likelihood of experiencing most individual symptoms and more than three or five symptoms at a time decreased after the first dose. Trends were mostly positive between the first and second doses, but most returned to a declining or flat trend after the second.
A clear explanation is “still lacking”
“People with long-lasting COVID who experience immune system dysregulation may benefit from ‘resetting’ autoimmune processes through vaccination (although the duration of this disease remains to be determined), while any residual viral reservoir can also be destroyed by the antibody response,” the authors wrote.
While the observational nature of the study precludes establishing a causal link, “vaccination may contribute to a reduction in the population health burden of long COVID,” they concluded.
In a related editorial, Manoj Sivan, MD, of the University of Leeds in England; Trisha Greenhalgh, MD, of the University of Oxford; Ruairidh Milne, MBBS, from the University of Southampton; and Brendan Delaney, BMBCh, of Imperial College London, said the results show vaccination is likely to avert long COVID in only a small percentage of patients.
“A clear explanation of how vaccines might reduce the multisystem manifestations of long COVID is still lacking,” they wrote. “Particularly for people who are already well past systemic inflammatory responses, and those with end-organ damage due to COVID-19, such as pulmonary fibrosis.”
Although the benefits of vaccination outweigh the potential risks and are particularly important for patients with long-term COVID, Sivan and colleagues said much remained unknown about the effects of recurrent infection or booster doses. and the long-term prognosis.
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