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As first appeared in The New York Times,


IT'S flu season, and health agencies have expanded their flu shot recommendations to include all children ages 6 months to 5 years in addition to adults over age 50, and anyone, child or adult, with a chronic condition like severe allergies, asthma or diabetes.

More parents than ever before - nearly 65 percent - intend to vaccinate their young children this year, according to a poll by the University of Michigan. But that leaves more than a third unenthusiastic about doing so. Their reluctance may reflect not only weariness with the increasing number of childhood immunizations but also the widespread sentiment that colds and flus are a "natural" part of childhood, even vital for toughening up a developing immune system.

Some parents have come to embrace colds and flus, and in recent years we've seen a resurgence of the chickenpox party, where parents deliberately expose their preschoolers to infected playmates on the theory that it's better to get the disease than to have the vaccine.

But the idea that illness is good for children - or anyone else - is wrong. In part, the idea of "good sickness" is a throwback to a now disproved version of the "hygiene hypothesis."

In 1989, an epidemiologist in Britain, David Strachan, observed that babies born into households with lots of siblings were less likely than other babies to develop allergies and asthma. The same proved true of babies who spent significant time in day care. Dr. Strachan hypothesized that the protection came from experiencing an abundance of childhood illnesses.

Dr. Strachan's original hygiene hypothesis got a lot of press, not only in the news media but in serious medical journals. Less publicized was the decade-long string of follow-up studies that disproved a link between illnesses and protection from inflammatory disorders like allergies and asthma. If anything, studies showed, early illness made matters worse.

Moreover, studies now show that the more infections a person has during childhood, the greater his or her chance of premature death from scourges of old age like heart disease and cancer. The link appears to be chronic inflammation, a kind of lingering collateral damage from the body's disease-fighting response.

Still, Dr. Strachan's original observation was confirmed - as a group, babies in large families and day care are less likely to develop allergies and asthma than are children born into smaller families and kept at home. The same protective effect can be seen in children born on farms and in areas without public sanitation.

But the link isn't disease-causing germs. It's early and ample exposure to harmless bacteria - especially the kinds encountered living close to the land and around livestock and other young children. In other words, dirt, dung and diapers. Just as disease-causing microbes clearly bring on inflammation, harmless microorganisms appear to exert a calming effect on the immune system.

A second misconception common among vaccine-shunning parents is that there's something "natural" about the 6 to 10 respiratory infections the typical American child gets every year (or even the two to four we adults experience). Common, yes; natural no, not if "natural" represents the forces that shaped the human immune system during all but the last sliver of our 250,000 years as Homo sapiens. Colds, flus and most other contagious diseases found a central place in our lives only after we and our domestic animals began crowding together in large settlements some 5,000 years ago.

Yet the most compelling reason to get a flu shot this year is a new and deadly threat - methicillin-resistant Staphylococcus aureus, or MRSA, a dangerous kind of staph that has been causing outbreaks of deadly pneumonia among the otherwise young and healthy, typically on the heels of the flu.

Unfortunately, we have no practical way to eradicate MRSA. About a third of us silently carry staph at any given time, and trying to eradicate MRSA or any other staph strain from a community of symptom-free carriers is difficult to impossible. Worse, the experts conclude, any widespread effort to do so is certain to breed greater drug resistance.
Flu shots don't guarantee protection from MRSA pneumonia. It can piggyback on other kinds of viral respiratory infections. But protecting yourself and your children from the flu may be the best way to reduce your family's risk.

Whether dealing with the flu, other "routine" infections or even the chickenpox, the message is the same: In a world abounding in harmless, even beneficial microbes, don't embrace the tiny fraction that can make you ill.

Jessica Snyder Sachs, the former managing editor of Science Digest, is the author of the forthcoming book "Good Germs, Bad Germs: Health and Survival in a Bacterial World."

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This page contains a single entry by JSS published on January 2, 2009 4:33 PM.

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