South African Scientists Explore Effectiveness of Omicron Vaccines

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Scientists in South Africa have started crucial work to assess how resistant Covid vaccines are to the Omicron variant which has been detected in more than a dozen countries since it was officially reported last week.

The variant carries dozens of mutations that are expected to alter the behavior of the virus, including its ability to cause infection and its ability to hide from immune defenses initiated by vaccines or a previous infection by an older variant.

Antibodies protect against viruses by erasing them and preventing them from infecting human cells. To do this, they must recognize particular parts of the virus. Most Covid antibodies bind to one of the virus’ three sites, but all are mutated in Omicron, which means that antibodies produced by vaccines or past infection may be significantly less effective.

Professor Penny Moore of the University of the Witwatersrand and the National Institute of Communicable Diseases of South Africa said “pseudoviruses” – harmless, unreplicated viruses used to model variants of the coronavirus – will be designed to carry Omicron mutations. These will then be exposed to the antibody-bearing blood plasma of people who have been vaccinated and those who have recovered from the Covid infection to see if they neutralize the virus.

His lab will assess the protection offered by the Oxford / AstraZeneca, Pfizer / BioNtech and Johnson & Johnson vaccines, while plasma testing of recovered patients will help shed light on the risk of re-infection with Omicron. Early reports from South Africa suggest re-infections are more common with Omicron than the Delta variant, but much more data is needed to be sure.

Moore’s results, which could be available in the next two weeks, are expected to provide some of the first lab evidence as to whether existing vaccines are enough to keep Omicron at bay, or whether manufacturers will need to produce an updated vaccine. But with Omicron carrying so many mutations, creating the pseudoviruses is not easy. “It will take a while to introduce so many mutations,” Moore said.

Further work on vaccine protection is underway at the African Institute for Health Research in Durban, where virologist Professor Alex Sigal is growing batches of live Omicron from people infected in the recent Gauteng wave in South Africa. Once it has enough to work, the variant will be tested against the blood plasma of people who have been vaccinated and people with some natural immunity after infection with Covid.

South African scientists were the first to report the Omicron variant to the World Health Organization on November 24. At the time, the first known infection was on November 9, but earlier infections could come to light as countries investigate further cases, mostly among travelers who have recently returned from the region.

The work in South Africa is part of an urgent global effort to understand the threat posed by Omicron. Ravi Gupta, professor of clinical microbiology at the University of Cambridge, hopes to join the effort soon, first with pseudoviruses, then with live Omicron. Further experiments, he said, will examine how well synthetic antibody treatments treat the variant. Therapies are crucial for patients who are unable to develop their own immune response to the virus.

Several vaccine manufacturers have also started studies on the protection of jabs against Omicron. AstraZeneca analyzes infections and vaccination status of residents of Botswana and Eswatini, on the borders of South Africa. Meanwhile, a spokesperson for Pfizer said the company hopes to have the first results of its own antibody studies “in the coming weeks.”

While the variant largely eludes vaccines, Moderna and Pfizer say they can produce a new bespoke vaccine in about 100 days, subject to regulatory approval.

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