Intermediary Prevention

Intermediary prevention is a term I just hereby coined! It lies between primary prevention and secondary prevention. As I described in my two previous posts on prevention, the primary type is employed to prevent exposure to the disease causing agent and boost one’s resilience through lifestyle practices and public health measures in order to prevent illness from taking hold. Secondary prevention is used as a means of catching disease at an early stage after it has taken hold but before it is symptomatic in order to prevent it from progressing. This new category I am creating is for clinical interventions intended to assist us in resisting disease. Common examples of intermediary intervention are vaccinations, dietary supplements, contraception, and personal protective equipment such as seat belts, helmets, masks, gloves, and bullet proof barriers. These don’t prevent exposure to causative agents but they can decrease the exposure and/or increase our resistance to the potential harm.

Vaccinations expose us to a less potent form of a disease causing infectious agents or a portion of the microscopic organism. The injection is like an introduction to the infection so that if we encounter the more potent form or the full microbe we can mount an immune response more quickly and thus defend our body from the disease. As a side note, however, most vaccines have never been tested under randomized double blind controlled trials to see if they actually prevent morbidity and mortality (disability or death) from the disease they are intended to prevent. Most vaccines today are approved based on the assumption that if the body is able to increase antibody production to a portion of the virus or bacteria then probably it will prevent disability or death. This is a rational biologically plausible assumption. And experience has shown us that the polio vaccine, the small pox vaccine, the measles vaccine have indeed been effective in decreasing the population burden of these terrible illnesses. Yet, in the age of evidence based medicine it must be stated there is no strong evidence that many of our routine vaccinations prevent illness, disability, or death even if they do increase antibody production. Since we don’t know if they are effective we also cannot say whether they are cost effective. Many of the diseases that vaccination intends to avert in individuals could be prevented in larger groups of people through clean water and sanitation, changes in work and school policies, safe sex and drug use practices, screening of blood supplies, and other public health, political, economic, and cultural changes. We’d likely get more bang for our buck through these actions versus the immense effort required to vaccinate every individual on the planet. Stay tuned for a Nei Jing Now episode or short clip on the subject of vaccinations.

Dietary supplements are an intervention very often used as a means of intermediary prevention. As we know lots of money is spent on dietary supplements in the hopes of preventing disease and death, to the tune of 25 billion dollars a year in the USA alone. Most of these supplements have also not been proven effective in randomized double blind controlled trials and many come replete with their own cadre of side effects, some of which can be serious and severe. In Europe dietary supplements must be shown to be safe, though not necessarily effective, prior to marketing with health and nutrition claims. In the USA, dietary supplements are regulated by the Food and Drug Administration as food products, not as medicines. Again, they must be shown to be safe, but not necessarily effective. In fact, claims about preventing, treating, or mitigating disease are not allowed on supplements in the USA. In Asia, anything goes. The deteriorating quality of our food due to the industrialization of agricultural practice, the depreciation of our soil quality, the pollution of our water sources may indeed be factors to consider in our need to supplement our diets. Yet, we currently do not have sufficient scientific knowledge to replicate nature’s subtlety in regards to dosage and the dynamic complex interactions with other elements at play. Restoring the nutritional value of our food supply and revising our culinary cultural practices is likely to have a greater impact in preventing disease than dietary supplements for all.

Some dietary supplements are meant to be therapeutic, in which case they are classified as tertiary prevention interventions. (I’ll describe tertiary prevention more thoroughly in another post. In a nutshell it is the attempt to prevent death and disability by treating a disease after it has already become symptomatic.) Deficiencies of iron, vitamin D, vitamin B12, and others are treated with supplementation. This is not considered a preventive measure, but rather a therapy. Many therapeutic interventions from Traditional Chinese Medicine, Ayurveda, Naturopathy, and Homeopathy are labeled as dietary supplements.  These should be considered medicines and should only be taken under the advice of a trained or licensed practitioner. Their effectiveness and toxicities can be similar to Allopathic medicines. I would not classify these remedies under the intermediary prevention category since they are intended to treat diseases not prevent them.

The Office of Dietary Supplements at the National Institute of Health has accurate, up to date,
scientific information on many supplements that can help you make an informed decision about dietary supplement use. Stay tuned for a future Nei Jing Now series on the subject of dietary supplements.

The use of personal protective equipment is an example of an intervention that increases one’s capacity to resist the exposure to a toxic substance, infectious disease, chemical, fume, gas, chainsaw, hammer, or bullet. It doesn’t, however, decrease the presence of the injurious element. Most forms of contraception do not decrease engagement in the behavior that increases the risk of pregnancy. However, contraception is an intervention that does decrease the chances of pregnancy by either acting as a piece of personal protective equipment or decreasing the probability of fertilization. Vasectomy might be considered a primary prevention measure as it would decrease exposure to sperm, though not the risky behavior. Terminations would have to be considered secondary prevention of an unwanted pregnancy.

These are just examples of intermediary prevention.  There are many more. Strategically, intermediary prevention is more foresighted than secondary prevention and requires more expense and effort than primary prevention.  All tiers of the prevention pyramid are important. Currently we place much more importance and invest many more resources into secondary and tertiary prevention. If we emphasize primary prevention and devote more energy and attention in the lowest tier of the pyramid we could save ourselves a lot of effort, expense, and suffering in the long run. Nei Jing Now!