First Real-World Data Suggest Omicron Illness May Be Less Severe

December 16, 2021

Adults infected with the Omicron variant are 29 percent less likely to enter the hospital than people infected with other COVID-19 strains, according to the first large-scale real-world clinical data.

Discovery Health, the largest private insurer in South Africa, released both clinical and immunologic data from more than 211,000 tested subjects, 78,000 of whom were positive for the Omicron strain, on Dec. 14. It paints a picture of a much more transmissible, but potentially less lethal, illness.

The new data were released just a day after lab results were publicized, showing that Johnson & Johnson’s vaccine booster provides limited protection against the Omicron variant even as the Pfizer/BioNTech booster, a mRNA-based shot, appears to provide stronger protection.

“Epidemiological tracking shows a steep trajectory of new infections, indicating Omicron’s rapid spread, but so far with a flatter trajectory of hospital admissions, possibly indicating lower severity,” said Andrew Noach, Discovery’s CEO.

He cautioned against extrapolating the data to global populations. A large portion of South Africans have already been infected with COVID-19 and their existing antibodies could have lessened their Omicron illness. Nevertheless, this first glimpse at clinical outcomes is a positive one.

Those adults who were hospitalized with Omicron were not as acutely ill, said Shirley Haley, the company’s chief health analytics actuary. “Hospitalized adults currently have a lower propensity to be admitted to high-care and intensive-care units relative to prior waves,” she noted.

Children, however, seem to be at increased risk. “Children under age 18 have a 20 percent  higher risk of admission for complications of COVID-19 when infected with Omicron,” she said. The data are early and need follow-up, but they align with increases in pediatric admissions from June to September, including a more recent admission spike in children younger than five years.

However, Collie added, “Children were 51 percent less likely to test positive for COVID-19 relative to adults in the Omicron period and, overall, the risk of children being admitted to hospital for COVID-19 complications remains low.”

Despite these encouraging clinical signs, Omicron remains a serious threat, largely due to its extreme transmissibility and potential for reinfection. The analysis found that prior infection with the Wuhan, Beta and Delta strains doesn’t always protect against Omicron.

“Overall, the risk of re-infection has increased over time, with Omicron resulting in significantly higher rates of reinfection compared to prior variants,” Noach said. People who had been infected with Delta had a 40 percent risk of Omicron reinfection and those previously infected with Beta had a 60 percent risk of re-infection. — Michele G. Sullivan