The cumulative effect of viruses in day care

Tracy has a good question: “My 4 year old is not in day care – he stays with Granny. I heard that once you get a cold, you never get that cold again, and I am worried he isn’t exposed to enough germs now to keep him healthy later. Should we be trying to infect him with more colds now that he has the luxury of staying in PJs all day instead of hitting him with all these new viruses when he does start school?”

For many viral infections, it’s true: you get it once, you won’t get it again. Think about chicken pox, measles, or hepatitis A—suffer through the infection, or get the vaccine, and you’re pretty much protected for life. Second infections or breakthrough disease after vaccination can happen, but it’s uncommon. This doesn’t hold true for bacterial infections like pneumonia, whooping cough, or ear infections, but for many viruses immunity can last the rest of your life.

But the common cold isn’t caused by one virus, or even one family of viruses. Common cold symptoms occur with hundreds of kinds of rhinoviruses, coronaviruses, and the recently-discovered metapneumovirus, to name just a few. Each cold may earn you immunity from one variety of one virus, but there are plenty more of them lurking out there.

What about the cumulative effect of the dozens or hundreds of viruses on kids in day care? Do day care kids earn lasting protection from enough viruses to keep them healthier once they’re in school? And does that mean that kids who spent more time in their PJs with Granny will get sicker once they start kindergarten?

A study published in December 2010 tried to figure that out. Researchers followed about 1300 families in Canada over eight years to record the frequency of infections in children through their years of day care and school. They looked at upper respiratory infections, ear infections, and “tummy bugs” that caused vomiting and diarrhea. Their conclusion was actually quite satisfying: children, whether or not they attended day care, suffered through approximately the same number of infections over the course of the study. But day-care kids got more of their infections when they were younger, especially when they first started in group care, while kids who didn’t attend day care got more infections later when they started school. The piper gets paid, either way: get your infections over with early, or get them later.

It’s reassuring to know that overall, neither group of children was really sicker than the other. Whether or not children attend group care when they’re young doesn’t seem to affect the total number of infections, but rather only the timing of their infections. Parents can choose whether their children will get more infections now or later, but the total number of infections is going to be about the same either way.

Roy Benaroch is a pediatrician who blogs at The Pediatric Insider. He is also the author of Solving Health and Behavioral Problems from Birth through Preschool: A Parent’s Guide and A Guide to Getting the Best Health Care for Your Child.

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