It is too early for scientists to know much about the relationship between Omicron, vaccination and long COVID.
Many public health officials have taken heart in early evidence that suggests infections from the Omicron variant tend to cause less severe illness than other versions of the coronavirus. But another important question looms: whether infection with Omicron, including breakthrough cases in vaccinated people, can result in long COVID — the constellation of physical, neurological and cognitive symptoms that can last for months and impair people’s daily lives.
It is too early for scientists to know much about the relationship between Omicron, vaccination and long COVID. Research from earlier in the pandemic does not yield definitive clues. Here is a sketch of what scientists have learned and the many questions still to be answered.
Because the Omicron variant was first identified in late November, it is too early to say how long symptoms of infection can persist. It is also unclear whether, like previous versions of the virus, it can lead to the emergence of problems like brain fog or extreme fatigue after the infection has resolved.
Although recent reports suggest that Omicron may cause less severe initial illness than other variants, the basic symptoms of infection with Omicron are similar to infection with other variants, suggesting that long-term effects could also be similar. Milder initial illnesses do not necessarily mean that Omicron is less likely to lead to long COVID, doctors, researchers and patient-led groups caution. Studies from earlier waves of the pandemic indicate that many people who had mild or asymptomatic initial reactions to coronavirus infection went on to develop long COVID that persisted for months.
Can vaccines prevent long COVID? Maybe. Vaccines primarily prevent people from getting seriously ill or dying from a coronavirus infection. With some previous variants, vaccines seemed to reduce the likelihood of infection itself — and not being infected is, of course, the best way to avoid long COVID. But vaccines have not been as effective in preventing infection with Omicron, and breakthrough infections with this new variant are far more common.
Studies looking at vaccinated people and long COVID have so far mostly focused on data collected before the emergence of the Delta variant. And the study results have been mixed. One large study, which was published in the journal The Lancet Infectious Diseases, was based on reports to a phone app by more than 1.2 million British adults who had received at least one dose of a coronavirus vaccine between December 2020 and July 2021. It found that people who had received two vaccine doses and gotten breakthrough infections were about half as likely as people who had not been vaccinated to report symptoms lasting at least 28 days after their infection. About 5 percent of those with breakthrough infections reported such lingering symptoms, the study found, compared with 11 percent of infected people in an unvaccinated control group.
Another large study, which was published without being peer-reviewed, found a similarly encouraging result. The study, produced by Arcadia, a health care data firm, and the COVID Patient Recovery Alliance, a collaboration of leaders with health expertise in government and the private sector, analysed records of about 240,000 patients infected with the coronavirus by May 2021.
It found that people who had received even one dose of a COVID vaccine before their infection were seven to 10 times less likely to report two or more symptoms of long COVID 12 to 20 weeks later.
