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Omicron Variant Has Higher 'Asymptomatic Carriage', Suggests Studies From South Africa

Omicron Variant Has Higher 'Asymptomatic Carriage', Suggests Studies From South Africa
The Omicron variant of the coronavirus possessed a much higher rate of "asymptomatic carriage" when compared to the earlier variants of the virus which would be an explanation of the very high speed of its spreading throughout the world, showed preliminary findings from two South African clinical trials.
One of the studies was carried out when there was a surge in Covid-19 infections caused by the Omicron variant in South Africa last month while the other one resampled participants at about the same time. Both the studies found that the number of people testing positive for the coronavirus was much higher than earlier variants but showed symptoms that were different from what was experienced in the case of the previous trials.
In the Ubuntu research which evaluated the efficacy of Moderna's Covid-19 vaccine among HIV-infected persons, 31 per cent of 230 subjects tested positive for the virus, with all 56 samples available for sequencing analysis confirming that they were Omicron.
"This is in stark contrast to the positivity rate pre-Omicron, which ranged from less than 1% to 2.4 per cent," the researchers said in a statement.
The mean asymptomatic carriage rate climbed to 16 per cent during the Omicron outbreak from 2.6 per cent during the Beta and Delta outbreaks in a subgroup of the Sisonke study investigating the efficacy of Johnson & Johnson's Covid-19 vaccine.
"The Sisonke study included 577 subjects previously vaccinated, ... with results suggesting a high carriage rate even in those known to be vaccinated," the researchers said.
They added that the "higher asymptomatic carriage rate is likely a major factor in the rapid and widespread dissemination of the variant, even among populations with high prior rates of coronavirus infection".
From late November, when its scientists informed the globe to Omicron, South Africa experienced a spike in Cvoid-19 cases. However, new instances have since decreased, and early signs suggest that this wave was characterized by less serious disease than previous waves.

Christopher J. Mitchell

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