Adults vaccinated against COVID-19 were about 20 to 50 percent less likely to develop long COVID amid the Omicron wave than they were during the delta period, with variability by age and time since vaccination varied.
The find comes from a case-control observational study Published this week in The Lancet by researchers from Kings College London. The study found that about 4.5 percent of Omicron breakthrough cases resulted in a long-term COVID, while 10.8 percent of Delta breakthrough cases resulted in a long-term condition.
While the news may seem a little reassuring to those nurturing a groundbreaking Omicron infection, overall it’s cold consolation for public health given the Omicron variant coronavirus is much more transmissible than Delta.
“Far more people were first infected with Omicron than Delta,” said Kevin McConway, a professor emeritus of applied statistics at the Open University, in a statement. “So even if the percentage of those infected who had long COVID during the two waves is in the range these researchers are reporting — and it may well be — the actual number of people reporting COVID long after they report is first infected during the Omicron period, still much larger 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 first infected during the Delta Period.
The researchers, led by Claire Steves, a senior clinical lecturer at King’s College London, defined long COVID as new or persistent symptoms four weeks or more after the onset of acute COVID-19, as defined in the US National Institute for Guidelines for Excellence in the health and care sector.
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 percent to 50 percent. Chances were best when people were about to be vaccinated (within less than three months) and were 60 years 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 the long-running COVID cases. There was also insufficient data to examine long rates of COVID in unvaccinated individuals, and the study did not include data on rates in children.
The study was also conducted during the BA.1 wave, noted David Strain, clinical senior lecturer at the University of Exeter Medical School, in a statement. Subsequent omicron subvariants, including BA.2, BA.2.12.1, and the emerging BA.4 and BA.5, may have different long-COVID risk profiles.
Yet even if the 4.5 percent estimate holds up over time, it means many people are long developing COVID. This “creates a significant public health burden from this disease with no known treatment or even a reliable diagnostic test,” Strain added.
Steves echoed the sentiment, saying in a statement: “The Omicron variant appears to cause COVID-19 for significantly less time than previous variants, but still 1 in 23 people who contract COVID-19 have symptoms for more 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 workplace [National Health Service].”
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