Omicron variant risks infecting vaccinated people, may not cause severe illness – with insight from The Wall Street Journal

“Our message is: Don’t freak out, the plan remains the same: Speed up the administration of a third booster shot,” Dr. Sahin said in an interview 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 since 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 assumed that immunized people would have a high level of protection against severe disease even if infected by the Omicron variant.

Dr. Sahin said that the vaccine, which he and his team invented in January 2020 and then developed together with Pfizer Inc., has been proven to protect from severe disease against other variants of the coronavirus 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 of vaccination, 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 appeared 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.

“Our belief [that the vaccines work against Omicron] is rooted in science: If a virus achieves immune escape, it achieves it against antibodies, but there is the second level of immune response that protects from severe disease—the T-cells,” he said.

“Even as an escape variant, the virus will hardly be able to completely evade the T-cells.”

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, stressing that it would take time for patient data to confirm this.

Some experts are more skeptical. Dr. Sahin’s comments come after Moderna Inc. Chief Executive Stéphane Bancel told the Financial Times that he expected that 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 were “gratuitous and without any proof.”

Dr. Plotkin said that data so far indicated that antibodies played a key role in protecting from coronavirus, and that there was little evidence that T-cells would be fully protective against severe symptoms.

“Antibodies are clearly the major correlate of protection and we have little evidence that in the absence of antibodies the T-cells will do the job,” Dr. Plotkin said. 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.

“It makes sense for the virus to want to infect as many people as possible without killing them,” Dr. Plotkin said.

Other experts, however, agreed with Dr. Sahin. Professor Luke O’Neill, an immunologist and chair of biochemistry at Trinity College Dublin in Ireland said Dr. Sahin’s assumption made 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 had to be accelerated and said that the arrival of Omicron would most likely establish a three-shot vaccination as the optimal protocol for immunization against coronavirus.

It could take weeks for collated patient data to reveal the impact of Omicron on the vaccinated people it does infect. So far, scientists and doctors in South Africa, in the region where the new variant was first detected, said that around 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. “All of those things make it really hard to compare that population with ours.”

The BioNTech-Pfizer vaccine was originally administered in two shots, but in recent months many countries, including the U.S., started offering a third, so-called booster shot after studies showed that people who had received three doses had significantly stronger immunity.

Dr. Sahin welcomed this week’s decision by U.K. authorities to offer the third dose to all adults only three months after they had received the second shot.

“The U.K. firmly believes that the third shot offers even better protection, and that’s why it brings it forward,” Dr. Sahin said.

Dr. Sahin estimated that bringing an adjusted vaccine to market that specifically targets Omicron would take about 100 days, but said that this might not be necessary.

“We have a plan to administer a third shot to people, and we must stick to this plan and speed it up. Whether or not we will need extra protection by an adapted vaccine, this remains to be seen, later,” Dr. Sahin said.

It is too early to say whether populations would need to be vaccinated regularly for the foreseeable future to maintain a high degree of immunity, he said.

Appeared in the December 1, 2021, print edition as ‘BioNTech Says Vaccine Likely Fights Omicron.’