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Omicron With More Infections, Less Hospitalizations Than Delta, South African Data Show

Steven Li, MD
Steven Li is a medical professional with a passion for lifelong learning and spreading truth to the world. He specializes in the fields of health and science.
Published: December 20, 2021
Data from a South African Health Insurer shows Omicron is so far more infectious but resulting in less hospitalizations.
The passenger of a flight from South Africa is tested for the Coronavirus at Amsterdam Schiphol airport on December 2, 2021 in Amsterdam, Netherlands. Data presented by Discovery Health, a South African private health insurer, shows Omicron is so far more infectious but, producing less hospitalizations. (Image: Pierre Crom via Getty Images)

Recent data presented at a Dec. 14 briefing by South African private health insurer Discovery Health revealed that the Omicron Coronavirus Disease 2019 (COVID-19) variant “is spreading faster than any previous coronavirus variant and showing signs of immune escape, with both vaccinated and previously infected people more at risk than in previous waves.”

Over 90 percent of the sequenced infections in South Africa are the Omicron variant.

Increased infectivity

Protection against infection and severe symptoms has waned considerably for the COVID-19 vaccines, with the Pfizer-BioNTech vaccine offering only “33% protection against infection in this omicron fuelled wave, found the analysis, down from 80% in South Africa’s last, delta fuelled wave.”

Protection against severe disease and hospitalization has waned to 70 percent in the current wave, compared to 93 percent in the last wave.

Omicron has also infected those who had a previous COVID-19 infection, as new cases are “73% as common among the previously infected as among the never infected.” Analysis of the data was conducted in collaboration with the South African Medical Research Council.

The data spanned a period from Nov. 15 to Dec. 7. Over 211,000 COVID-19 tests were performed, and 78,000 were deemed Omicron cases. 41 percent of the tested individuals were fully vaccinated with the Pfizer-BioNTech vaccine.

According to the U.S. Centers for Disease Control and Prevention (CDC), the Omicron variant was first reported to the World Health Organization (WHO) on Nov. 24., 2021 from specimens in South Africa. The variant was deemed a Variant of Concern (VOC) on Nov. 26, and the first case of Omicron was confirmed in the U.S. on Dec. 1.

The CDC states, “Fully vaccinated people who become infected with the Omicron variant can spread the virus to others,” and due to “the small number of cases, the current severity of illness and death associated with this variant is unclear.”

However, the CDC says that compared to Delta, Omicron may spread more easily.

Decreased risk of hospitalization

The South African researchers found that despite the increased infectivity of Omicron, infections were 29 percent less likely to result in hospital admission compared to previous surges in South Africa.

Shirley Collie, a Discovery Health statistician, stated, “Adults admitted to hospital currently have a lower propensity to be admitted to high care and intensive care units, relative to prior waves.”

Although hospitalization of children has increased by 20 percent, “These cases are mostly mild and the absolute risk in children remains low.” Chief executive of Discovery Health, Ryan Noach, said. 

“We are hopeful that the current experience of covid-19 caused by the omicron variant—mild disease for the most part—will remain unchanged.”

During the Dec. 14 briefing, WHO director for Africa, Matshidiso Moeti, added, “We are cautiously optimistic as we are seeing fewer deaths during the early weeks of this current wave when compared with previous surges.”

According to a study conducted by University of Hong Kong researchers, which has not yet been published or peer-reviewed, Omicron “replicates 70 times faster than delta in human bronchus, but 10 times slower than delta in human lung tissue.”

The authors believe that the faster replication in the bronchus could explain increased transmission between humans, while the slower replication in the lungs “may be an indicator of lower disease severity.”

One of the authors of the study, Michael Chan Chi-wai, stated, ‘‘It is important to note that the severity of disease in humans is not determined only by virus replication but also by the host immune response to the infection, which may lead to dysregulation of the innate immune system, i.e. ‘cytokine storm.’” 

In other words, even if Omicron does not replicate as quickly, an overly aggressive immune system response could still result in severe symptoms.

Dr. Chan said, “By infecting many more people, a very infectious virus may cause more severe disease and death even though the virus itself may be less pathogenic. Therefore, taken together with our recent studies showing that the Omicron variant can partially escape immunity from vaccines and past infection, the overall threat from [the] Omicron variant is likely to be very significant.”