Vaccines could still protect against Omicron via powerful ‘T cells’ that are hard to measure but prevent severe illness and death

• Early data suggests Omicron could evade some types of protection from vaccines.
• Most has been about antibody responses, with less attention to another mechanism: T cells.
• T cells could stop the worst ravages of Omicron, but may not stop mild infection.

As studies and predictions flood in about the Omicron coronavirus variant, much attention has focused on the prospect that vaccines won't work as well against it.

Nations have thrown up travel bans, issued dire warnings, and supercharged their booster programs in the hope of holding back the new strain.

However, much of the warnings and decision-making do not address the fact that the body has two distinct ways to protect from a virus, and so far only one of those might be found wanting against Omicron.

Early research suggests that Omicron might be able to get around the human immune system's first line of defense — the antibodies produced either after infection or vaccination.

But there are signs that its backup force of so-called T cells, also primed after infection or vaccination, may yet provide a strong defense.

In a lab, Omicron escapes antibodies from vaccines

When a new variant comes to the fore, scientists run a series of tests in a lab to try and determine its characteristics.

The quickest is a test that analyzes how well antibodies fare against a virus, so that's usually the one the world hears about first.

Those tests are what drove recent news headlines warning that even two doses of vaccine may be insufficient.

Early lab data found antibodies in those with two doses of Pfizer vaccine working markedly less well against Omicron, producing an effect 25 to 40 times weaker than with other variants.

This could be because Omicron's dozens of mutations make it harder for existing antibodies to do their job of recognizing patterns on the virus and attacking them.

Enter the T cell

The way T cells behave in the body takes much longer to work out. They patrol the blood and are meant to pounce and kill the virus, a reaction that does not require effective antibodies.

They too learn from previous infection and vaccination and it could be that their effect remains intact with Omicron

Early research published in a non-peer-reviewed study and accompanying press release from Pfizer and BioNTech said that Omicron's mutations might not affect the ability of T cells to confront it.

"It suggests that T cell responses remain largely intact and should remain largely intact against Omicron," Andrew Redd, a virologist at the National Institute of Allergy and Infectious Diseases said, per NBC news.

The issue with T cell responses, however, is that they are slower to act than neutralizing antibodies, Eric Topol, founder and director of the Scripps Research Translational Institute, said in a blog post.

This means that, while it may ultimately help the body defeat the virus, it could allow a mild infection to develop first, and could allow sick people to spread the virus, Topol said.

"It should, I hope, keep the majority of infected people from having to go to the hospital," Rachel Graham, an assistant professor in the department of epidemiology at the University of North Carolina at Chapel Hill, told NBC news.

Boosters could bring antibody levels back up

At this stage, there's not enough data to say for sure how these mechanisms function in the context of Omicron.

Early real-world data from South Africa, published Tuesday before peer review, suggested that two doses of Pfizer vaccine seemed to have reduced the risk of hospitalization by about 70% even at a time when Omicron was a majority of cases. This compares with rates of about 90% for the Delta variant.

Experts, however, warned that it is too soon to conclude how effective vaccines are against Omicron from this data alone, Insider previously reported.

Early company data suggests that boosters may enhance the level of protective antibodies against Omicron, at least in countries where the shots are available.

According to data mentioned in a Pfizer press release, which had not been released to the public, boosters caused a 25-fold increase in neutralizing antibody levels after two doses of vaccine, bringing them back up to levels seen with earlier variants.

The World Health Organization has said that there is not enough data to say that boosters are necessary for most.

The Centers for Disease Control, however, recommends eligible adults should be getting boosters.