The Covid vaccines could still protect against omicron, even if it evades antibodies — here's how

Omicron is officially in the United States — and the country's approved Covid vaccines could already contain a key to fighting it.

On Wednesday, public health officials confirmed the country's first known case of Covid's omicron variant, detected in California. The individual, who is fully vaccinated but not boosted, traveled from South Africa to San Francisco on Nov. 22 and tested positive on Nov. 29.

The person has mild symptoms that appear to be improving, and none of their close contacts have tested positive so far, White House chief medical advisor Dr. Anthony Fauci said in a briefing Wednesday.

The case bolsters growing — though unconfirmed — concerns among scientists that omicron might be able to skirt the antibodies that you get from Covid vaccines, at a higher rate than other variants.

But crucially, that's no reason to avoid getting vaccinated or boosted: Your body's vaccine-induced protection against Covid involves a lot more than just antibodies. And one of those other forms of protection, T cells, could keep fully vaccinated people from getting severely sick — even if they do catch omicron.

It might even explain why the patient in California only has mild symptoms. Here's why.

How vaccine-induced T cells add a layer of Covid defense

When you get vaccinated against Covid, your immune system produces an arsenal of weapons — including different types of immune cells, like antibodies, memory B cells and T cells — that work together to fend off the virus.

The antibodies are your body's first layer of defense. They bind to and coat the surface of the virus to prevent it from invading a cell, effectively keeping you from getting sick in the first place.

T cells are the next layer. These white blood cells, also known as lymphocytes, target and destroy cells infected with a virus. A subset of T cells, called killer T cells, are particularly effective because they seek out and annihilate infected cells, stopping the infection from spreading and keeping you from getting severely sick.

All three of the country's approved Covid vaccines prompt your body to create T cells, and research suggests that those vaccine-induced responses remain strong in the face of Covid mutations — even gnarly ones that can escape antibodies.

That's essentially what some experts are counting on right now. On Tuesday, for example, BioNTech CEO and co-founder Dr. Ugur Sahin told the Wall Street Journal that omicron will have a tough time escaping the "second level of immune response" conferred from T cells.

Others say that without quantifiable data, it's too soon to know exactly how well T cells will hold up to omicron. Kristian Andersen, an immunologist at the Scripps Research Institute, told STAT on Wednesday that while T cells will be able to respond to the virus, it's not yet clear how effective they'll be at protecting against transmission and infection.

If omicron proves too problematic for the current vaccines to handle, variant-specific vaccines could be on the horizon. The Biden administration is already planning with Pfizer, Moderna and Johnson & Johnson for that potential contingency, White House Covid coordinator Jeff Zients said in a briefing Tuesday.

Moderna says it's working on a reformulated vaccine that could be ready to ship by early 2022, if necessary. J&J also says it's working on a new omicron-specific vaccine, while Pfizer says it's waiting for more data before acting.

In the meantime, Fauci recommended two actions for everyone to take, during a White House Covid Response Team briefing on Tuesday: Get your Covid vaccine and booster when you're eligible, and keep following the mitigation methods you've been using since the pandemic began.

That includes masking, hand hygiene, distancing in indoor public spaces and isolating when necessary.

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