The Omicron variant has triggered a new wave of the COVID-19 infection across the world. The new variant was first detected in South Africa in November last year and within very short duration it spread throughout the world leaving medical fraternity high and dry.
Studies are now being conducted to understand the variant better as it seems to be highly transmissible. Preliminary findings from two clinical trials in South Africa suggest that this variant has a higher rate of asymptomatic 'carriage' than earlier variants.
Both studies on Omicron found a higher rate of infection than during previous outbreaks, and a higher proportion of asymptomatic carriers. One of the studies that was carried out when Omicron infections were surging in South Africa and another which resampled participants around the same time, found a far greater number of people tested positive for the virus but were not showing symptoms.
In the Ubuntu study, 31% of 230 participants undergoing screening tested COVID-19 positive. All 56 samples available for sequencing analysis were verified to be Omicron.
"This is in stark contrast to the positivity rate pre-Omicron, which ranged from less than 1% to 2.4%," the researchers said in a statement.
In the sub-study of Sisonke, the mean asymptomatic carriage rate rose to 16% during Omicron period from 2.6% during Beta and Delta outbreaks.
The results suggest a high carriage rate even in those vaccinated, the South African Medical Research Council said in a release.
The Sisonke study included 577 subjects previously vaccinated with results suggesting a high carriage rate even in those known to be vaccinated.
Higher asymptomatic carriage rate is likely a major factor in the rapid and widespread dissemination of Omicron, even among populations with high prior rates.