Free-riding microbes: stronger, more powerful, and our fault

June 5, 2000
Web posted at: 3:38 p.m. EDT (1938 GMT)

In this story: Vaccines and the problem of free riders The false comfort of 'sterile' lives RELATED STORIES, SITES

The American Medical Association recently held a press briefing to talk about a basic public health issue: the spread of infectious disease and how our behaviors miss the boat when it comes to protection and prevention of illnesses spread by microbes. One of the more impressive successes of public health has been the recognition and control of the germs that cause infectious diseases. But some of our current practices -- skipping vaccinations for children, overusing antibiotics and antibacterial household products -- threaten to undo these great strides. These actions may seem to benefit the individuals who "enjoy" them, but they may be creating future public health disasters.

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The vaccination of populations can be effective only if a high proportion of at-risk individuals receive vaccines.

High rates of vaccination lead to what is known as "herd immunity," which occurs when so many members of a group are immunized that it becomes impossible for infectious disease to spread. When herd immunity exists, it means the risk of diseases like mumps, measles or whooping cough are so reduced that people can forego vaccination with little worry of the consequences -- at least for themselves.

But this sort of free riding on the backs of those who undergo vaccination is both unfair and dangerous.

First, it is unfair because it takes advantage of the responsible behavior of others. The only reason some can afford to go without vaccines is because the majority do the right thing.

What's even more troubling is that people often avoid immunizing their children because they perceive vaccines to be risky. But a pool of unvaccinated children creates a real risk for the entire community, since it lays the foundation for new epidemics. In fact, declines in vaccination rates in some European countries have led to recent measles outbreaks, with some associated deaths. A decision to forego vaccination means putting personal benefit ahead of collective benefit, but turns out to undermine both in the end.

The false comfort of 'sterile' lives

Even as fewer people seek vaccinations -- in part because they believe that they are safe without them -- there has been a widespread increase in the use of antibacterial soaps and sprays at home, and parents and patients demand antibiotics at every sign of infection. These efforts at sterilizing our hands and countertops, and at killing every infection in our bodies can have just the opposite effect.

Unless we soak our tables for many minutes and scrub our hands like surgeons, we can't kill all the bacteria on our skin, and what is left behind to survive and multiply are the stronger and more resistant germs. Our overuse of antibiotics has helped foster more numerous and stronger antibiotic-resistant microbes, to the point that we're running out of "last line" drugs to fight even the most resistant bacteria.

The inconsistency between the unwillingness to use vaccines and the overuse of germ-killing drugs, soaps, and sprays can be explained in part by our focus on the individual and what we can each control. It's an example of putting individual needs ahead of the collective good, and of putting short term thinking ahead of long term concerns. Such is human nature, and we can see it in many areas of society, whether in decisions about medical care or environmental conservation.

But infectious disease forces us to think differently. We want polio and smallpox to remain controlled diseases, to feel confident that our children won't be part of a measles epidemic, and know that there are antibiotics that will fight even the most difficult infections. But these successes require that we all take on some risk as individuals to serve both our collective and individual needs in the long run.

This will be one of the 21st century's important health challenges, and is an example of Benjamin Franklin's admonition that "We must indeed all hang together, or most assuredly, we shall all hang separately."