Among adults vaccinated against COVID-19, the odds of developing long COVID in the middle of the omicron wave were about 20-50% lower than in the delta period, with variability based on age and gender. time elapsed since vaccination.
The finding comes from an observational case-control study published this week in The Lancet by researchers at Kings College London. The study found that approximately 4.5% of omicron breakthrough cases resulted in long-term COVID, while 10.8% of delta breakthrough cases resulted in long-term illness.
While the news may seem a bit reassuring to those treating an omicron breakthrough infection, it is hardly comforting to public health as a whole since the omicron variant of the coronavirus is much more transmissible than the delta.
“Many more people were first infected with omicron than with delta,” Kevin McConway, professor emeritus of applied statistics at the Open University, said in a statement. “So while the percentage of infected people who got long COVID over both waves is on the scale that these researchers are reporting – and it may well be – the actual number of people reporting long COVID after being infected for the first time during omicron is still much greater than during delta.”
For The Lancet study, researchers looked at self-reported symptom data from 56,003 UK adults who were first infected with SARS-CoV-2 during the omicron wave and 41,361 UK adults who were initially infected during the delta period.
The researchers, led by Claire Steves, clinical lecturer at King’s College London, defined long COVID as having new or persistent symptoms four or more weeks after the onset of acute COVID-19, as defined at the US National Institute for Health and Care Excellence Guidelines.
When the researchers adjusted for age, time since vaccination, and other health-related factors, the relative odds of developing long COVID after omicron ranged from about 23% to 50%. The odds were better when people were closer to vaccination (less than three months old) and aged 60 or older.
The study has limitations, the most obvious of which is that it is based on self-reported symptom data and does not delve into the severity of long COVID cases. There was also insufficient data to examine long COVID rates in unvaccinated people, and the study did not include data on rates in children.
The study was also carried out during the BA.1 wave, as David Strain, clinical lecturer at the University of Exeter Medical School, noted in a statement. The following omicron subvariants, including BA.2, BA.2.12.1, and promising BA.4 and BA.5, may have different profiles regarding long-term COVID risks.
Yet even if the 4.5% estimate holds over time, it translates to many people developing long COVID. This “creates a significant public health burden of this disease with no known treatment, or even a reliable diagnostic test,” Strain added.
Steves echoed that sentiment, saying in a statement, “The omicron variant appears significantly less likely to cause long COVID than previous variants, but 1 in 23 people who get COVID-19 continue to have symptoms for longer than four weeks Given the number of people affected, it is important that we continue to support them at work, at home and in the [National Health Service].”