Q&A: Immunity for non-experts

Why do you find the prevailing public view of the immune system as either “strong” or “weak” (like a muscle)—deficient?

Fagan: The immune system isn’t only for defense! Its cells and pathways are connected with other body systems, including development and cognition, in ways we’re learning more about all the time. So, the starting premise for analogizing immunity with muscle is flawed; its role in the body is more complex.

Also, the immune system is too complex, too multi-faceted, to represent how it works on a simple continuum of “weak to strong.” That conflicts with our current scientific and philosophical understanding that the immune system is always active, always dynamically interacting with all our internal components and other systems, as well as the ways we interact with our environments. It doesn’t work like something you can turn up with a dial, just setting it to “stronger.”

What social problems does this misunderstanding contribute to?

Fagan: The main social problem I’m interested in is vaccine skepticism and hesitancy. Beyond the “strong vs. weak” framing, vaccines can appear— very reasonably, to a lot of people— as a violation of bodily autonomy, or as loss of authority over children.

There are other social forces and trends involved, one of which is distrust of science and of other powerful institutions. It also lends itself to profitable manipulations. You can sell people a lot on the promise of “stronger immunity.” Then, vaccines can appear to be another effort to sell you stronger immunity— this time by powerful government groups like the Center for Disease Control during the pandemic.

Related to that, if you assume that immunity works like a muscle, then, by analogy, it needs exercise to stay strong—it needs to face and overcome challenges, like pathogens. Vaccines might then look like an impure cheat, compared to wholesome, natural immunity from overcoming viruses on your own. Not everyone thinks the same way, so not everyone would make these connections. But they are straightforward associations to make, if you’re starting with the “strong vs. weak” framing.

In multiple ways, then, that framing contributes to a “cultural environment of distrust” around vaccines.

The YES schema

Can you walk us through the YES schema (immunity is Yours, Effective and Specific)? 

Fagan: Not to be redundant, but … YES!

One’s immune system originates with and develops alongside one’s life as a biological organism; it is inextricable from that life and, therefore, inalienably yours.

Of course, there is more to our lives than being biological organisms, but our immune systems keep us alive for all that. Nothing can “take over” your immune system or control it so it becomes less than wholly yours. (Something like bone marrow transplants might be an objection to this, but that’s a separate discussion, for a longer format.)

Your immune system is effective at solving problems that arise for you as a biological organism: sub-personal problems, one could say. This captures the breadth of the immune system’s activities, which go well beyond defense.

An organism’s life has a beginning, middle, and end. Solving an organism’s problems puts off the end, extending the middle. If you’re alive, your immune system is effective at solving those problems. It’s not perfect; nothing in the living world is. But it is effective and constantly at work.

Each living body has its problems, and your immune system works continuously to solve those in its purview. But we can’t forget that its effectiveness is specific. The ongoing, dispersed, multifarious activities of the immune system’s components converge into a specific response with targeted precision, like a trap springing shut.

A subset of dispersed immune “players” is rapidly recruited into a specific response, intricately orchestrated so as to maintain an organism’s healthy life in the face of a problem. The sharp, precise point of each immune response is the culmination of an immensely complex collection of interactions at multiple sites and times within the body.

Were other ideas considered in developing the YES schema and set aside?

Fagan: Yes, again!

My earlier versions were more abstract, centered on cell lineages and “stemness” (the property of being a stem cell). It was a topological image, a structure I thought of the immune system as having (there is still a “reverse bowtie” image associated with the “S” of the YES schema). [See Figure 1]

I also started with a narrower view of immunity, as just antibodies and B and T lymphocytes —white blood cells. So, the early version was another philosophical theory, missing some new insights from philosophy of immunology.

Then I learned about the “extended view of immunity,” not being all about self-defense, from that area of philosophy.

Finally, I brought in ideas from my latest book, on understanding across disciplinary boundaries. A lot of scientists and medical practitioners collaborate effectively with immunologists without understanding much about the immune system. The key move was to think of non-experts on immunology in a similar way. So, I do propose a philosophical theory linking immunology experts and non-experts, but it’s about how the two groups relate to each other, not adding a new technical model to the mix.

Effective problem-solving

"Effective" means the immune system solves problems for the organism. Isn't it more nuanced than a "fix-it" system? I’m thinking of malfunctions or collateral damage like that of healthy surrounding tissue while the system is fighting an infection.

Fagan: You’re right, “collateral damage” is common in immune responses. I think this feature fits well with “effective problem-solving” though. Depending on the problem, sometimes the solution has knock-on consequences that are themselves undesirable. Then one does one’s best to manage those. We’ve all been there.

The immune system, as we currently understand it, works like that too, at molecular, cell, and tissue levels. A lot of its complexity, many theorists believe, is to regulate and mitigate the collateral damage following from some immune responses. And some immune phenomena, like autoimmune diseases, highlight failures in a system that’s still effective overall. 

“Effective” doesn’t mean “no room for improvement.” (This leads us to vaccines, among other things.)

What role do you see the YES schema playing in addressing vaccine skepticism, and where are its limits?

Fagan: First off, the YES schema is at most a small part of any solution to this problem, and to anti-science more generally. It doesn’t directly combat deliberate misinformation campaigns, for example.

Here’s where I hope this schema can be of help. When clinicians are talking to patients about vaccines and those patients have concerns or anxieties about vaccines for themselves or their kids, the clinician could present the YES schema as a quick overview of what the immune system is and how it works. Then, what a vaccine is, is just a way to improve its efficiency for one specific response.

That’s it. The system is just speeding up one potential response, out of all its myriad ongoing activities.

Vaccines, as a technology, are effective because they do so little. They are an experimentally calibrated nudge that modifies ongoing immune system activity in one specific way.

Can the YES schema be used by the layperson?

Fagan: Non-experts can understand and explain YES just as well (maybe even better), so it’s not limited to clinical contexts. It would be good to have an alternative to the “strong vs. weak” conception of immunity, and the associated misunderstandings from thinking of it as analogous to, say, muscle tissue.

So, I hope the YES schema has the potential to spread. That could block the misunderstandings I noted above, that feed vaccine skepticism and related problems.

One important limitation to note is that trust isn’t part of the YES schema itself. The schema is just an accessible model of the immune system and how it works. But for that schema to be useful, to play the positive roles I’ve sketched out, there has to be some trust between the parties involved. Doctor to patient, or just to people in everyday contexts— conveying the YES schema as a tool for understanding won’t work without some trust in place. So that’s a major limitation, or a background condition, for this model.

Experts and non-experts

If a layperson’s understanding of the immune system is not a weaker version of an immunologist’s but just a different kind of understanding that serves different purposes, what does that mean for them in practice?

Fagan: The title of my paper is “immunity for non-experts.” My view exempts non-experts from having to learn immunology.

What this means in practice is that anyone can have a good understanding of the immune system that works for daily life, and connects to our best current scientific understanding, without walking the path toward expertise. That’s the best any of us can do, about most areas of knowledge today. Instead of aiming to transmit expert understanding to non-experts, we should try to connect our best current scientific and philosophical understanding of the immune system with everyday experience. The connection is about accessibility; making the science accessible to people whose lives and concerns are different from immunologists’.

What do experts gain from this exchange?

Fagan: That’s a really important question. I’m currently working on this, so what I’ve got now is a provisional answer, two answers, actually.

First, for clinicians working with patients, what I hope is that the YES schema can help their practice. Thinking about the physician-patient interaction as more a collaboration than a one-way transmission of information; that could make those interactions more effective and productive, on both sides.

My second answer is more abstract. I think the view of knowledge as had by an isolated, brilliant individual expert has reached its limit, in philosophy and society. Thinking about one’s own expertise as a brilliant node in a much larger, interconnected lattice—with the connections enhancing it—seems a better image for today. Connections with different kinds of understanding enhance one’s expertise—and give one a window on other areas of expertise, including ones that aren’t officially recognized or respected.

Thank you for sharing this research with us. One last question: could this approach work for other topics, such as climate science or genetics?

I hope so! The general approach is in my 2025 book. I would love to see these ideas tried out in different scenarios.