Even Symptom-Free, People With Omicron Much More Likely to Spread COVID: Studies

Monday, January 10, 2022 – Researchers said they’ve discovered evidence why the Omicron variant of COVID-19 is spreading much more quickly than its predecessors.

The data show that people who are infected but do not have symptoms are still more likely to be infected to others than they were with the previous variants.

“As we witness the rapid global spread of Omicron, it is clear that we urgently need to better understand the transmission dynamics of this variable,” said senior study author Dr. Lawrence Currie. He is the principal investigator in the Operations Center of the Fred Hutchinson Cancer Research Center of the COVID-19 Prevention Network.

“Because many people may be asymptomatic, we cannot always know who is carrying the virus, but we know what we can do to protect ourselves and to help prevent the spread of disease: wear a mask, wash your hands, avoid too much, indoor gatherings and fully vaccinate as soon as possible.” .

Both new studies were conducted in Africa.

The Sisonke study used PCR testing from mid-November 2021 to December 7, 2021, in people without symptoms. It found that the transfer rate was 16%.

The larger Ubuntu study found that 31% of transmission is asymptomatic, or in 71 of 230 samples between December 2 and December 17, 2021. All samples available for sequencing analysis have been verified as Omicron.

Previous studies on ancestral, beta and delta variants had asymptomatic transmission rates of 1% to 2.6%, seven to 12 times lower than the Omicron samples, the researchers said.

An Ubuntu study began in early December with the goal of evaluating the effectiveness of Moderna’s COVID-19 vaccine in people with HIV.

Sisonke’s research was a sub-study of a larger study that evaluated the effectiveness of a single dose of the Johnson & Johnson COVID-19 vaccine. The sub-study evaluated breakthrough immune and inflammatory responses in 1,200 health care workers, including those who are pregnant, nursing, or living with HIV. The study included 577 people who were vaccinated with the COVID-19 vaccine from Johnson & Johnson, and the results suggest a high rate of transmission even in those who have been vaccinated.

“The larger studies are designed to analyze data at the intersection of COVID-19, vaccines, and people living with HIV, but they also give us useful information about Omicron and how its prevalence differs from those earlier variables of concern,” Dr. Glenda Gray, chair of the South African Medical Research Council (SAMERC), said in a press release from the center.

Dr Nigel Jarrett, head of vaccines and HIV research at the South African AIDS Research Program Center, said sub-Saharan Africa has been hit hard by both the HIV and COVID-19 pandemic.

“Ubuntu and Sisonke will provide important data on vaccine safety, dosage, and efficacy, but they are already helping us better understand how this virus can change and how those changes affect its transmission and severity. It is critical to know how Omicron and others are spreading variables,” Jarrett said. Among those who are immunocompromised as well as among those who are not.

Preliminary results for both studies have been published on a prepress server medRxivand has not been subject to peer review.

“We have not yet been able to determine how vaccination affects asymptomatic infection and its spread,” said Linda Jill Baker, director of the Desmond Tutu HIV Center at the University of Cape Town. “We also need to devise strategies for rapid detection of asymptomatic transmission, particularly in long-term care facilities and hospitals, where transmission to high-risk populations may occur.”


  • COVID-19 Prevention Network/South African Medical Research Council Press release, 7 January 2022

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