In a new study from Fred Hutchinson Cancer Research Center, researchers found a clue to why the Omicron variant spreads COVID-19 so much more rapidly than its predecessors.
They found people who are infected but have no symptoms are still far more likely to infect others than they would have been with earlier variants.
In the study, the team used PCR testing from mid-November 2021 to Dec. 7, 2021, in asymptomatic people. It found the carriage rate was 16%.
The larger Ubuntu study found 31% asymptomatic carriage, or in 71 out of 230 samples between Dec. 2 and Dec. 17, 2021. All the samples available for sequencing analysis were verified to be Omicron.
Past studies on ancestral, Beta and Delta variants had asymptomatic transmission rates of between 1% and 2.6%, seven to 12 times less than with the Omicron samples, the researchers said.
In the study, the team evaluated immune responses and breakthrough infections in 1,200 health care workers, including those who are pregnant or breastfeeding or who have HIV.
The study included 577 people vaccinated with Johnson & Johnson’s COVID-19 vaccine, with results suggesting a high carriage rate even in those known to be vaccinated.
Sub-Saharan Africa has been hit hard by both HIV and the COVID-19 pandemic.
Researchers say that the findings provide important data on safety, dosage and effectiveness of vaccines, but they already are helping us better understand the way this virus can change and how those changes affect transmission and severity.
It is critical that scientists know how Omicron and other variants spread among those who are immunocompromised as well as those who are not.
The team says since so many people may be asymptomatic, people can’t always know who is carrying the virus.
But we 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.
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The study is published on medRxiv. One author of the study is Dr. Lawrence Corey.
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