They utterly changed the nature of infectious disease. Communicable diseases that had previously wiped out wide swathes of the population could be controlled with simple injections. Deaths dropped dramatically.

They became ubiquitous and virtually mandatory. The companies that manufactured them became extraordinarily wealthy and developed into large multinational conglomerates.

[pullquote align=”right” cite=”” link=”” color=”” class=”” size=””]It is easy for lay people to believe that antibiotics work, but it requires specialized knowledge to understand how vaccines work.[/pullquote]

But there were side effects. Some recipients suffered serious medical consequences. Some even died. Yet despite these dire consequences, they have remained a cornerstone of medical practice.

What are they?

If you thought I was talking about vaccines you are mistaken. I am referring to antibiotics. I want to talk about a curious paradox. Antibiotics and vaccines are the two most powerful and effective weapons against infectious diseases. Yet antibiotics are accepted without demur and vaccines are the subject of a variety of conspiracy theories. Why should they be viewed so differently?

Both are highly effective. Both are delivered by injection (though they can be delivered in other ways). Both have serious side effects including death. Both are manufactured by large multinational corporations who profit from their sale. So why are vaccines the subject of hysterical pseudo-scientific conspiracy theories, while antibiotics are not merely accepted as necessary, but actively sought, sometimes even when they are not needed?

There are four critical differences and those differences shed light on the nature of pseudo-scientific conspiracy theories. The differences tell us why certain conspiracy theories flourish and others are rejected out of hand.

The first difference is the ease of explanation. The workings of antibiotics are, on their face, easy to understand. Antibiotics kill bacteria by poisoning them. Everyone understands what a poison is and how it can be effective. We routinely poison weeds in our lawns, and mice in our homes. Poisons figure prominently in crime shows and detective novels. When patients are told that antibiotics will cure them by poisoning the bacteria that are making them sick, patients have no trouble understanding or envisioning how the antibiotics will do the job.

In contrast, the explanation of how vaccines work is rather complex. It requires familiarity with the notion of the immune system in general and antibodies in particular, how antibodies function in the body, and how they are created. This is not information that can be acquired in the course of every day life. We have no direct experience with eliciting antibodies to fight disease. Antibodies are certainly not subjects for TV shows or novels. Understanding vaccination, therefore, requires specialized knowledge not easily obtained.

The second difference is the time scale. Antibiotics work quickly, in hours or days at the most. We are sick, we take antibiotics, we get well. It is easy to credit the role of antibiotics in curing illness because they are temporally connected. Cure reliably follows the administration of antibiotics. It is easy to believe that the antibiotics cause the cure.

In contrast, vaccines act over long periods of time. Pertussis vaccine is give in infancy. Years go by and those infants become young children who never develop pertussis. The connection between vaccination and wellness is not directly apparent.

Third, there is something fundamentally different between curing a disease and preventing it. Curing a disease allows for certainty on the part of the person being cured. Connecting the absence of a disease with a maneuver designed to prevent it is not apparent to most people. There are other possible explanations besides vaccination for why a child does not get pertussis. He or she may never have been exposed. Some children who are exposed do not get the disease, even if they haven’t been vaccinated.

Fourth, there is a difference in apparent effectiveness. The reality is that a given antibiotic will never be 100% effective, but there are almost always alternatives. If penicillin does not do the trick, another antibiotic may be more effective. Ultimately, though, the patient is cured by antibiotics, whether it is the initial antibiotic, a subsequent antibiotic or a combination of antibiotics.

No vaccination is 100% effective, either, but there is usually one and only one vaccine for a particular disease. If the vaccine fails, the person gets the disease and there is no other vaccine that can be administered to prevent it.

These differences can be readily summarized: it is easy for lay people to believe that antibiotics work, but it requires specialized knowledge to understand how vaccines work. That’s why it’s not a coincidence that vaccine conspiracies flourish among those who lack basic knowledge of science, immunology and statistics. They literally cannot understand the issues involved. And if they can’t understand it, there is lots of room to disbelieve it and to substitute conspiracy theories for the truth.

This piece first appeared in November 2010.