The Ecological Fallacy

What’s true of a population isn’t true of any individual person in it. For example, a population has an average height. No single person is exactly that height. To confuse the two is to commit what is called the ecological fallacy.

A more serious example concerns a cornerstone of public health: vaccination against the flu.

The journal Science recently devoted an entire issue to the controversy surrounding two studies that were held up for publication because they described methods used to create highly pathogenic strains of influenza virus for the purpose of developing vaccines. Although the two studies were eventually published, the articles in the special Science issue explore the implications of such research.

In one article titled “Influenza: Options to Improve Pandemic Preparation,” the authors outline an aggressive program of vaccination. They advocate increasing the capacity to develop, manufacture, and deploy vaccines, including what they refer to as “universal” vaccination—meaning vaccination whether you want it or not. This is based on the generally accepted notion that flu spreads like wildfire through a population unless a large number of people are immune—so-called herd immunity.

I hope you won’t be surprised to know that the researchers work for Novartis, a major manufacturer of flu vaccine.

Let us suppose for a moment that the Novartis people are right and that the only way to avoid an influenza catastrophe is to vaccinate everyone. In other words, vaccination is good for the herd. But would it be good for you?

Some smart scientists argue that vaccination can cause Guillain-Barré syndrome, narcolepsy in children, and accelerated onset of Alzheimer’s disease. It also happens that people vaccinated can still get the flu. For all those people, vaccination isn’t such a good thing.

The word from the CDC is that vaccines are perfectly safe: everyone should get them, especially two groups of people. The first group consists of people at risk of developing respiratory complications (people with asthma, diabetes, or lung disease), women who are pregnant, and people older than 65. The second group consists of the people who take care of people in the first group.

But there’s more. In a recent review of the scientific literature, researchers found that there is no evidence to support the claim that vaccination prevents flu in people 65 and older. In another recent review, researchers found no evidence to support the claim that the vaccination of caregivers prevents flu in people 65 and older.

In other words, the groups that the CDC says are at risk and therefore in need of vaccination might not be at risk at all. Still, some people might benefit from vaccination: that the herd didn’t benefit doesn’t mean that an individual person won’t.

Unfortunately, there’s research to suggest that the biological theory supporting vaccination is wrong.

Your immune response has two systems: the innate and the adaptive. Innate immunity is your body’s response to creatures and chemicals that are foreign to it and therefore potentially harmful. Inflammation, for example, is an innate immune response.

Innate immunity activates adaptive immunity, which is the world of antibodies. When an unknown bacteria shows up in your body, your innate immune system isolates it and attempts to eliminate it. As a consequence your adaptive immune system develops a specific biochemical—an antibody—to attack the bacteria the next time it shows up.

Vaccines short-circuit this process by “training” the adaptive immune system to develop those antibodies. So the development of vaccines by corporations such as Novartis are a big guess about what the next influenza virus will look like so the right chemicals can be developed for the vaccine that will be injected into your or your loved one’s body thereby training your adaptive immune system for the onslaught.

As it turns out, your immune system doesn’t respond to viruses that way. Your body responds with the innate immune system—which doesn’t need to be trained at all (Moseman et al., 2012). What your innate immune system does need is a healthy body to support it.

Even if the folks at the CDC and the folks at Novartis believe deeply in the efficacy of flu vaccination based on what they think is true of the herd, that’s not a good reason for you to be vaccinated because those folks have committed the ecological fallacy. Of course, if things go their way, you might not have a choice.