A major factor behind the Omicron variant’s rapid and widespread circulation even in vaccinated people.
Omicron appears to have a much higher asymptomatic carriage rate than earlier COVID-19 strains, studies suggest.
This may explain why Omicron spreads so rapidly across populations causing higher rates of infection relative to other coronavirus variants.
Asymptomatic carriage is when infected individuals with COVID show no symptoms but pass the disease along.
The increased Omicron asymptomatic carrier rate has led to far greater numbers of coronavirus cases even in the vaccinated.
A South African study has found that asymptomatic carriage during Beta and Delta outbreaks was 2.6 percent while this rose to 16 percent for Omicron, suggesting a 7 times higher infection rate.
Dr Lawrence Corey, the study’s senior author, said:
“As we witness the quick, global spread of omicron, it is clear that we urgently need a better understanding of the transmission dynamics of this variant.
Since so many people may be asymptomatic, we can’t always know who is carrying the virus, but we do know what we can do to protect ourselves and to help prevent further spread: Wear a mask; wash your hands; avoid large, indoor gatherings; and get fully vaccinated as soon as possible.”
Researchers from Hong Kong University found that the Omicron reproduction rate in the human lung was 10 times slower than the Delta variant, while 70 times faster than Delta in the bronchus.
The study has not been published yet but their findings indicate that Omicron is spreading faster but causes less severe disease than Delta.
However, Dr Michael Chan Chi-wai, the study’s lead author, cautioned:
“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.
Given its ability to partially escape immunity from vaccines and past infection, the overall threat from the omicron variant is likely to be very significant.”
The study was published in Medrxiv (Garrett et al., 2021).
