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Among the many unknowns surrounding long COVID is if and how the condition may arise with different SARS-CoV-2 variants.
A new statistical bulletin from the U.K. Office for National Statistics (ONS) takes a look at the risk of long COVID after an initial infection compatible with the Delta, Omicron BA.1, and Omicron BA.2 variants.
The analysis focuses on individuals who have not previously experienced a SARS-CoV-2 infection and compared double-vaccinated with triple-vaccinated individuals. Triple vaccination included third and booster doses.
The analysis found that in triple vaccinated individuals, there was no statistically significant difference in the risk of long COVID among the considered variants.
Dr. Daniel Ayoubkhani, the ONS’s principal statistician and co-author of the analysis, told Medical News Today that the statistics offered insight into the long COVID risk with Omicron variants.
“We believe this is the first published evidence to date on the epidemiology of long COVID following infection with the Omicron variant, and there is now a need for further research into the possible biological mechanisms behind our findings.”
— Dr. Daniel Ayoubkhani
The statistical bulletin was posted on the ONS website.
The analysis revealed some differences in long COVID risk among recent SARS-CoV-2 variants.
Double-vaccinated individuals with initial infections compatible with the Delta variant were 50.3% more likely to report long COVID symptoms than those who experienced COVID-19 with the Omicron BA.1 subvariant.
The data also found that the risk of long COVID in those whose infections were compatible with Omicron BA.1 and BA.2 was not quite the same.
For triple-vaccinated individuals, the odds of developing long COVID symptoms were 21.8% higher for Omicron BA.2 compared to Omicron BA.1.
“Among triple-vaccinated adults, we estimate that approximately 1 in 15 people first infected with the Omicron BA.1 variant will report long COVID symptoms four weeks after infection, rising to 1 in 12 people first infected with the Omicron BA.2 variant,” said Dr. Ayoubkhani.
The bulletin’s authors socio-demographically adjusted the data to eliminate as many potentially confounding variables as possible before performing their final calculations.
Dr. Ayoubkhani and co-author Dr. Matt Bosworth, senior research officer at ONS, note in the bulletin that their primary analysis considered reported long COVID symptoms of any severity.
However, they also looked into reports of more serious symptoms and found that “there was no statistical evidence of a difference in the likelihood of activity-limiting long COVID between the Omicron BA.1 and BA.2 variants.”
The bulletin reinforces the sense that Omicron may not be as concerning as previous variants.
“Omicron may replicate more readily in the upper airways than the lungs, potentially indicating a biological mechanism for a reduction in the risk of severe consequences following infection with Omicron variants compared to Delta,” Dr. Pouwels said.
He also noted that “one could speculate [a] third vaccination provides better protection against severe outcomes than two vaccinations among those without previous infection. However, it may also be simply waning of effectiveness as more time passes since your most recent vaccination.”
It may also be the case, according to Dr. Pouwels, that the analysis considered only those who have not experienced previous COVID-19 infections, “an increasingly smaller part of the population now.”
Drs. Ayoubkhani and Bosworth analyzed fresh “experimental statistics,” meaning that the data is still being tested and developed.
It is also self-reported data, based on individuals describing their long COVID symptoms. Such data is not necessarily reliable, since it depends on individuals’ recollections and subjective impressions. However, in the case of investigations into long COVID, there currently may be no better choice available.
Dr. Ayoubkhani explained:
“Published research in the U.K. has demonstrated that recording of formal long COVID diagnoses is low and variable between primary care practices. Self-reported symptoms are therefore the only way at present to estimate the prevalence of long COVID in the population.”
The analysis tracked long COVID symptoms from four to eight weeks after an initial infection, noted Dr. Koen Pouwels, senior researcher for Oxford Population Health, who collaborated with Drs. Ayoubkhani and Bosworth.
“I think it is… important to realize that the report is focusing on reporting of long COVID symptoms four to eight weeks after a first SARS-CoV-2 infection, while long COVID is often defined as having at least 12 weeks of symptoms compatible with long COVID,” he said.
“With more data becoming available over time, we will repeat the analyses using the standard definition of 12 weeks,” he told MNT.
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