| In this week's edition of the Covid Q&A, we look at long Covid and viral variants. In hopes of making this very confusing time just a little less so, each week Bloomberg Prognosis picks one reader question and puts it to experts in the field. This week's question comes to us from Laura in St. Louis Park, Minnesota. She asks:
Are people experiencing long Covid at the same rates with the new variants as they were at the beginning of the pandemic? First up, a big disclaimer. Two years into this seemingly never-ending pandemic, long Covid is still poorly understood. Generally speaking, there are more questions than answers — regardless of variant. Far more resources and studies will be needed to better understand how to treat and prevent persistent symptoms of Covid-19. "Estimates of vaccine effectiveness against long Covid have varied from 15% up to 50%, again because of differences in research methodology," says Katrine Wallace, an epidemiologist at University of Illinois at Chicago.  Research suggests that long Covid may be less prevalent after an infection with the omicron variant. Photographer: Lam Yik Fei/Bloomberg A large retrospective study published last week of over 2 million patients' medical records in the US found that 1 in 5 Covid survivors age 18 to 64 experienced at least one condition that might be attributable to previously having Covid. For those 65 and up, it was 1 in 4. (Wallace notes a caveat: None of those published studies present results separately for people with a booster shot.)
In other words, long Covid is still affecting many people.
But, says Wallace, we're starting to get some insight into how variants play into this picture. "Recent estimates of the prevalence of long Covid do seem to suggest it is less common after the omicron variant than other previous variants like delta," she says.
The latest UK Office for National Statistics Coronavirus Infection Survey bulletin, for example, looked at the risk of long Covid symptoms after an initial infection with the delta, omicron BA.1 and omicron BA.2 variants. It found that among people who hadn't previously been infected, the odds of a Covid symptom four to eight weeks after a BA.1 infection was about 50% less common than with the delta variant in adults who were fully vaccinated. Similarly, a study preprint released this month from another small survey from a Japanese clinic also found less long Covid with omicron than other variants. Judging prevalence of long Covid is difficult, Wallace says, because the research studies that have been undertaken have used different criteria for evaluation. More studies will help us better understand the role that booster shots — as well as treatments like antiviral medications — might play in treating and preventing lingering symptoms.
"The best recommendation that is supported by the data would be to get boosted to prevent not only severe Covid, but also long Covid from the omicron variant," says Wallace. "Because omicron is so transmissible, we will have more cases, and thus more long Covid just by nature of the increased number of infections."
Thanks to all of you for writing in this week! Next Sunday, we'll be answering the best question we receive again. So if you have any, we want to hear from you. Write to us at CovidQs@bloomberg.net —Kristen V. Brown | 
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