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Everything we know about Omicron based on early data in South Africa


South Africa is seeing a flatter trajectory of hospital admissions compared to previous waves, ‘indicating likely lower severity’ — but there are caveats

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As each day passes, panic seems to be spreading about what the Omicron variant is going to mean. The head of Ontario’s COVID-19 Science Advisory table has cautioned against “wishful thinking” that Omicron truly causes milder illness, Atlantic Canada has tightened restrictions to stop the variant’s spread and modellers in B.C. are predicting Omicron could cause the highest infection rates the province has seen by early January. But the first preliminary, real-word study out of South Africa offers optimism, mixed with prudent caution — yes, Omicron is highly contagious, but South Africa is seeing a flatter trajectory of hospital admissions compared to previous waves, “indicating likely lower severity,” investigators said Tuesday. The insights are preliminary, based only on the first three weeks of the Omicron-driven wave in South Africa, and may change as the wave progresses, they stressed. But here is what they are reporting:

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What did the study involve?

The analysis by Discovery Health, South Africa’s largest private health insurance administrator, was based on more than 211,000 positive COVID-19 test results, 41 per cent from adults who had received two doses of the Pfizer-BioNTech vaccine. About 78,000 of these test results were due to Omicron infections between Nov. 15 and Dec. 7.

The researchers looked at the Pfizer vaccines’ real-world effectiveness against hospital admission from Omicron infection. They also looked at the risk of reinfection for people who have had a previous COVID infection, and the risk of hospital admission among adults and children infected with Omicron.

What do the early findings show?

People infected with Omicron appear less likely to develop severe disease than adults infected during the first wave of COVID in South Africa. The risk of hospital admission was 29 per cent lower for adults.

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The reduction in severity is encouraging and suggests an “apparent de-linking” of the infection curve from the admission curve, according to a slide presentation presented at Tuesday morning’s press briefing. While infections rose rapidly during the first three weeks of South Africa’s Omicron wave, “admissions and deaths are not increasing as rapidly.”

Still, “we should not be lulled into any type of complacency,” said Dr. Ryan Noach, CEO of Discovery Health.

One key caveat: South Africa has a high rate of background immunity. In Gauteng, the province where Omicron was first identified in November, 72 per cent of the population is thought to have been previously infected, especially during the Delta wave. Other countries could have a different epidemiology picture, Shabir Madhi, a vaccinologist at the University of the Witwatersrand, told Bloomberg. Even with less severity, a surge in infections could have the capacity to overwhelm hospitals. In Canada, 76 per cent of the population is fully vaccinated.

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Children younger than 18 seem to have a 20 per cent greater risk of hospitalization but, in absolute terms, the admission of children to hospital remains very low. “There is no reason to panic in this regard, without question,” Noach said.

Again, anecdotal reports suggest most COVID infections in children admitted to hospital are being picked up incidentally, during routine screening, when children are admitted for problems unrelated to COVID. Children were also 51 per cent less likely than adults to test positive for COVID during the study period.

Most children have mild symptoms such as sore throat, congestion, headache and fever, symptoms that usually resolve within three days.

How effective is Pfizer at holding off Omicron?

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Two doses of Pfizer-BioNTech provides 33 per cent protection against COVID-19 in the current Omicron wave, a significant drop from the 80 per cent protection against infection in earlier waves. But the vaccine appears to be providing 70 per cent protection against severe complications requiring admission into hospital. “Whilst protection against hospital admission reduced from the highs of 93 per cent in South Africa’s Delta-driven variant, 70 per cent is still regarded as very good protection,” the investigators said. And the protection held across all ages, in people ages 18 to 79.

For people previously infected with COVID, the risk of reinfection is significantly higher compared to earlier variants — people infected with Delta face a 40-per-cent relative risk of reinfection with Omicron, the data suggest. It could be due to waning antibodies.

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How fast is Omicron spreading?

South Africa is seeing a steep trajectory of new infections, “indicating very rapid spread,” Noach said. “This is clearly a highly contagious variant of SARS-CoV-2.” According to Ontario’s science advisory table, the doubling time for the variant is approximately every three days.

What does infection with Omicron look like?

Anecdotal reports suggest “nuanced” differences in the features, for people both in and out of hospital, Noach said. It appears to have a shorter incubation period (three to four days). A scratchy or sore throat is the most common early symptom, like earlier waves. Other typical features include nasal congestion, dry cough and muscle aches and pains, especially lower back pain.

People seem to be experiencing less respiratory distress, the proportion of ICU admissions are lower compared to previous waves and a significantly lower proportion of people admitted to hospital require oxygen support, according to the data, which have not been peer reviewed.

Sixteen per cent of ICU admissions were among the vaccinated, according to raw data.

National Post

 

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