"The Omicron variant of the Covid-19 virus could lead to more infections among vaccinated people, according to several scientists, but some said there were reasons to believe the shots would protect against severe disease.
While the new variant might evade the antibodies generated in reaction to the vaccines, the virus likely will remain vulnerable to immune cells that destroy it when it enters the body, said Ugur Sahin, co-founder of BioNTech SE, which sells a Covid-19 shot with partner Pfizer Inc.
"Our message is: Don't freak out, the plan remains the same: Speed up the administration of a third booster shot," Dr. Sahin said Tuesday.
It will take a couple of weeks for scientists working for the main vaccine makers to determine through laboratory tests whether antibodies generated by the existing shots are effective against the new variant. Later on, data collected from patients will reveal how often vaccinated people infected with Omicron go on to experience mild or severe Covid-19 cases.
So far, there are few confirmed infections involving the new variant, making it difficult to generalize findings from these cases, especially because it can take weeks for Covid-19 patients to develop severe symptoms after they become infected.
Still, based on current knowledge about the mechanisms behind the vaccines and the biology of variants, Dr. Sahin said he assumes that immunized people would have a high level of protection against severe disease even if infected by the Omicron variant.
Dr. Sahin said the shot, which he and his team invented in January 2020 and developed with Pfizer, has been proven to protect against severe illness from other coronavirus variants that infect vaccinated people.
The currently prevalent variant, Delta, has proven more adept at infecting vaccinated people than earlier variants but those people mostly experience only mild symptoms, Dr. Sahin said.
The vaccine developed by BioNTech and Pfizer, like most other vaccines, offers two distinct layers of protection against the virus. The first comprises antibodies, which may help prevent people from becoming infected in the first place by preventing viruses from colonizing healthy cells in the body.
Antibodies, however, start to wane around five months after the second dose, according to some studies. Due to the high number of mutations, Omicron is likely to be better at circumventing the antibodies generated after contact with the vaccine than Delta, Dr. Sahin said.
This characteristic of Omicron may explain why preliminary tests suggest that an antibody drug cocktail from Regeneron Pharmaceuticals Inc. isn't as effective against Omicron as against older variants, the company said Tuesday. Outside scientists said another antibody drug cocktail from Eli Lilly & Co. also appears to lose effectiveness.
Vaccines also provide a second layer of protection: Immune agents called T-cells, some of which mobilize to destroy infected cells after an infection has occurred.
"Even as an escape variant, the virus will hardly be able to completely evade the T-cells," Dr. Sahin said.
That means that, even if the vaccines are shown to be less effective at neutralizing the Omicron variant, they could still offer good protection against severe disease and death, Dr. Sahin said.
Some experts are more skeptical. Dr. Sahin's comments come after Moderna Inc. Chief Executive Stephane Bancel told the Financial Times that he expects the current Covid-19 vaccines would be less effective at tackling the Omicron variant.
Stanley Plotkin, a veteran scientist who developed a number of vaccines, including the shot against rubella, said Dr. Sahin's assumptions are "gratuitous and without any proof."
Dr. Plotkin said data so far indicates that antibodies play a key role in protecting from coronavirus, and that there is little evidence that T-cells would be fully protective against severe symptoms.
However, he said it would make evolutionary sense for mutations in the virus that make it more infectious but less deadly to human hosts to become dominant over time.
Other experts, however, agree with Dr. Sahin. Professor Luke O'Neill, an immunologist and chair of biochemistry at Trinity College Dublin in Ireland said Dr. Sahin's assumption make sense from an immunological point of view.
"There is optimism that the T-cells will hold the line -- they are very good at stopping severe disease," he said. Even so, he said the booster campaign must be accelerated, and added that the arrival of Omicron would most likely establish a three-shot vaccination as the optimal protocol for immunization against coronavirus.
So far, scientists and doctors in South Africa, in the region where the new variant was first detected, said that about three out of four people currently hospitalized in the country were unvaccinated, while others had received only one dose.
Experts cautioned that the overall number of patients so far remains too small -- and their infections too recent -- to draw firm conclusions on whether Omicron leads to milder or severe cases of Covid-19 than other variants.
Peter English, a retired consultant in communicable-disease control in the U.K., cautioned that researchers would also want to see data in their own countries because the South African population is younger on average than many Western countries and has a relatively low rate of vaccination." [1]
1. U.S. News: Omicron Risks Infecting Vaccinated People
Pancevski, Bojan. Wall Street Journal, Eastern edition; New York, N.Y. [New York, N.Y]. 01 Dec 2021: A.6.
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