Half of People Infected With Omicron May Not Have Known It: Study

WEDNESDAY, Aug. 17, 2022 (HealthDay News) -- Are you one of those folks who thinks they have somehow miraculously managed to avoid COVID-19 infection more than two years into the pandemic?

You might be mistaken, claims new research that discovered most people hit by the highly contagious Omicron variant had symptoms so mild they didn't know they were infected.

A full 56% of those infected weren't aware they had COVID-19, researchers report. Earlier studies had found that as many as 80% of those infected never experienced symptoms.

"These findings help to confirm what we have suspected for some time, which is that many COVID infections are not being detected or recognized — in part because they are not resulting in a lot of symptoms and in part because there is limited access to or use of diagnostic testing," said lead researcher Dr. Susan Cheng. She is with the department of cardiology at the Smidt Heart Institute of Cedars-Sinai Medical Center in Los Angeles.

"Most people with COVID being unaware of their infection status, especially while actively transmissible, is likely a major driver of the ongoing pandemic that we are all still trying to make our way through," she added.

For the study, Cheng's team took blood samples from health care workers, and in 2021 they were also able to collect blood samples from patients. That part of the study was funded by Sapient Bioanalytics, which tested the samples for the virus.

The researchers had nearly 2,500 health care workers and patients contribute blood samples just before or after the start of the Omicron surge.

They identified 210 people who were infected with the Omicron variant. Only 44% of these people were aware that they had been infected. Of those who were unaware, only 10% said they had symptoms, which they attributed to a common cold or other infection.

"More than half of people who developed Omicron infection were unaware of their infection. In most cases, they had mild or no symptoms. In the few instances where there were mild symptoms, these symptoms were attributed to some other cause, such as a common cold," Cheng said.

To try to beat the pandemic, it's vital that people know that they can have COVID-19 and not have any or only mild symptoms, but still spread the infection to others, she stressed.

"Increasing infection awareness could help a great deal to curb the ongoing spread of COVID across our communities," Cheng said. "Because infection awareness rates appear to be low, there is tremendous room for improvement. We now have the tools to achieve this improvement, and we can each do our part to, hopefully, get through this pandemic faster and together."

Infectious disease expert Dr. Marc Siegel, a clinical professor of medicine at NYU Langone Medical Center in New York City, said this study clearly shows that COVID-19 has infected many more people than has been reported.

"There's a heck of a lot more mild or asymptomatic or very, very mildly symptomatic COVID out there than we're acknowledging, and that means that we're getting a lot of immunity at least to this variant," he said. "That might help explain the overall picture of the current state of the pandemic, which is that there's a lot of mild cases, but there's also a lot of severe cases."

Siegel thinks the immunity one gets from the virus has been underplayed.

"It's especially important now when we're seeing how easily transmissible this thing is," he said. "We know we're undercounting. When I see 100,000 cases a day, I think it's really a million cases. We're getting to the point where the vast majority of people in the United States have had COVID in one form or another."

The combination of immunity from the virus itself and that gotten from vaccination may help slow the pandemic, Siegel said.

Vaccination is important in preventing severe disease, especially among those most at risk. "I'm encouraging patients to get boosted to decrease the risk of hospitalization," he said.

Soon, Siegel expects to see new vaccines that will be more effective than the current crop, including nasal vaccines and universal coronavirus vaccines.

The report was published online Aug. 17 in JAMA Network Open.

More information

For more on COVID-19, head to the U.S. Centers for Disease Control and Prevention.

SOURCES: Susan Cheng, MD, MPH, department of cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles; Marc Siegel, MD, clinical professor, medicine, NYU Langone Medical Center, New York City; JAMA Network Open, Aug. 17, 2022, online