Data analysis indicates omicron is milder, better at evading vaccines
CBC
The omicron variant appears to cause less severe disease than previous versions of the coronavirus, and the Pfizer vaccine seems to offer less defence against infection from it but still good protection from hospitalization, according to an analysis of data from South Africa, where the new variant is driving a surge in infections.
While the findings released Tuesday are preliminary and have not been peer-reviewed — the gold standard in scientific research — they line up with other early data about omicron's behaviour, including that it seems to be more easily transmitted.
A two-dose Pfizer-BioNTech vaccination appeared to provide just 33 per cent protection against infection during South Africa's current omicron wave, but 70 per cent protection against hospitalization, according to the analysis conducted by Discovery Health, South Africa's largest private health insurer, and the South African Medical Research Council.
The data was gathered from Nov. 15 to Dec. 7, during which time omicron was first spotted by scientists in South Africa and Botswana, and may change as time passes.
Researchers around the world are rushing to figure out what omicron will mean for the coronavirus pandemic, now well into its second year.
Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization (VIDO) at the University of Saskatchewan, said the early analysis from South Africa around vaccine protection is promising.
"The 70 per cent protection against severe disease is really encouraging and also consistent with what we're seeing with other variants," she said.
"It's not surprising that that would be the case as well for omicron because the part of the immune system that is thought to mediate disease severity is less likely to be affected by all of these mutations."
In the weeks since omicron was detected, South Africa has experienced rapid spread of the virus — concentrated in its most populous province, Gauteng.
The seven-day rolling average of daily new cases in the country rose over the past two weeks from 8.07 new cases per 100,000 people on Nov. 29 to 34.37 new cases per 100,000 people on Dec. 13, according to Johns Hopkins University. The death rate hasn't increased during that same period.
"The omicron-driven fourth wave has a significantly steeper trajectory of new infections relative to prior waves. National data shows an exponential increase in both new infections and test positivity rates during the first three weeks of this wave, indicating a highly transmissible variant with rapid community spread of infection," Noach said.
Although case numbers are rising, hospitalizations are not increasing at the same rate, leading the scientists to report that the risk of hospitalization from omicron is lower than delta or earlier variants.
Rasmussen said we shouldn't assume the risk of hospitalizations from omicron will be similar in Canada.
"In Ontario, for example, we're already seeing a very steep upward curve in the number of cases. Hospitalization and death are both lagging indicators of severity, meaning that it will be a couple more weeks before we have an idea if omicron is going to behave the same way in Canada," she said, adding that doing anything to reduce transmission including booster shots and mask mandates beyond provincial mandates are needed.
