person receiving a COVID vaccine

Public health experts are recommending everyone gets vaccinated and gets a booster if they qualify. But Omicron, the new COVID variant, has been in the news for potentially evading the vaccine. So why even bother getting vaccinated or boosted now that Omicron is here in Dane County?

The answer is that your immune system isn’t an on/off switch: it’s a dimmer switch. We don’t know everything about Omicron yet. Omicron might dim the lights a little bit, but we likely won’t be in a power outage. But how does this work exactly?

This content is modified from the Science Vs. episode “Omicron: Do You Need to Freak Out?” For more information, please listen to the full episode or read the transcript. Thank you to Dr. David O’Connor’s research team and Dr. Thomas Friedrich’s research team for help in writing and fact checking this blog post.

Memory B cells: Your Elite Fighter Squad

There are lots of parts to our immune systems, and lots of kinds of cells that respond to foreign invaders (like viruses or bacteria). One important part of that system are your memory B cells, which help create antibodies that participate in the fight against viruses.

When you get vaccinated, your body receives instructions to make a piece of the surface of the COVID virus called the spike protein. This spike protein can’t get you sick on its own and is the key to your body recognizing the COVID virus in the future. When the spike protein enters your bloodstream, your body recognizes it as an invader and sends your immune system into action, sending B cells to create antibodies that bind to the spike protein and mark it for destruction.

What comes next is a fierce competition between B cells. The very best B cells create antibodies that can latch strongly onto the spike protein. The B cells that can’t produce strong enough antibodies die off, and the best B cells continue to train and train until they can create great antibodies. Some B cells are stored in your bone marrow for future use, and some continue to patrol your bloodstream, ready for the next time your body comes across the COVID spike protein.

When COVID mutates, not all parts of the spike protein change

An important point is that each memory B cell recognizes only a small part of the spike protein. Think of the spike protein like the “face” of COVID. Some B cells might have gotten really good at remembering what its ears look like, while others know its eyes best. Every B cell knows a portion of the overall picture of COVID’s face.
The B cells in your immune system remember different parts of the COVID virus spike protein. So even if some parts of the spike protein change, some of your B cells will still be able to create antibodies that can attach to the virus!

Variants like Delta and Omicron have changes to the spike protein. In Delta, this meant that some memory B cells didn’t recognize it, causing more breakthrough infections in people who were vaccinated. But enough B cells recognized it and produced antibodies to prevent vaccinated people from getting very sick. (Vaccines also stimulate T cells, another type of immune cell, that also help protect from severe illness.)

For Omicron, it’s likely that at least some of your B cells will recognize it. Because there are lots of changes to the spike protein in Omicron, some B cells probably won’t recognize the spike protein, but others probably will. So training your immune system with a vaccine isn’t useless—it’s actually really important to make sure you have your fighter squad of B cells and T cells ready to go. Even if only some of your B cells are useful in battle, wouldn’t you rather have some defense instead of zero defense?

Boosters are essential, especially with Omicron

Even if you are vaccinated, it’s very important that you get a booster shot as soon as possible once you are eligible. Think of a booster as a “refresher course” for your immune system. Getting a booster shot will increase the number of memory B cells ready to respond, which can help combat the “dimming” effect of Omicron. Even if some of the memory B cells you have can’t recognize Omicron, you’ll also be pumping up the ones that will. So get a booster shot as soon as you can!

A final question you might have: what if I already got COVID? Don’t I have memory B cells? The answer is yes, but they can be more variable in quality than the ones you get from a vaccine. Early research about Omicron suggests that people with past COVID infection who are not also vaccinated may be at high risk of catching Omicron. So it is still valuable to get your vaccine and/or booster, even if you previously had COVID.

The conclusion: get vaccinated and boosted

We don’t know everything about Omicron yet, but we know that immunity isn’t an all-or-nothing game. It is still very important to get vaccinated and boosted. The vaccine is the best tool we have to fight COVID, even Omicron.

This content is free for use with credit to the City of Madison - Public Health Madison & Dane County and a link back to the original post.