Following primary infection, the varicella-zoster virus becomes latent in the dorsal root ganglia. Reactivation of the virus, probably related to a decline in specific cell–mediated immunity, results in clinical herpes zoster (shingles). This common condition causes significant morbidity, especially chronic neuralgia, in older patients. Thomas and colleagues tested the hypothesis that frequent exposure to the virus through contact with children could repeatedly boost immunity and decrease the incidence of shingles.

They studied patients who had recently been diagnosed with shingles by physicians in 22 general practices in London. Each patient was matched by age and sex with two control subjects from the same practice. All study participants were interviewed to establish their level of contact with children younger than 10 years (the most common group with varicella infections in the United Kingdom). Participants were grouped into three categories—distal, intermediate, and proximal—based on the duration and frequency of contact with children.

The 244 patients and 485 control subjects were well matched, with only an average of five days difference in age. Positive history of contact with cases of varicella during the previous 10 years was found to be strongly protective against shingles, even after adjusting for all contacts with children. Protection against shingles increased with exposure to many children outside the home, and there was some evidence of a dose-response effect.

The authors conclude that continuous exposure to varicella virus through community contacts protects latently infected adults from developing clinical shingles. This correlates with reports that children with leukemia show immunologic boosting and reduced rates of clinical shingles after exposure to varicella cases. The effect of living with children appeared to protect against shingles by increasing total exposure to large numbers of children outside of the household. Because of immunization, the authors speculate that lower rates of childhood varicella could lead to increased rates of adult shingles as the virus becomes less prevalent in the community. In the long term, however, vaccinated persons are less likely to develop latency, so rates of shingles would eventually fall.

editor's note: Several friends from the baby-boomer generation have endured shingles over the past few years, but none has developed post-herpetic neuralgia, possibly because of aggressive antiviral therapy. One patient was initially considered to have atypical angina, and only the appearance of the rash after 36 hours of unusual chest pain spared him from intensive cardiac evaluation. This article raises the prospect of a mini-epidemic of shingles in the generation who were all exposed to chicken-pox as children and whose immune systems are now aging gracefully. Perhaps it is time to seriously consider varicella vaccination at midlife. If all of our other immune protections are fading, maybe grandparents should take infants for their shots and physicians should offer “twofers.” An alternative would be the approach to rubella encountered during my Scottish childhood. A large party was held at the home of the first case, and all the little girls in the neighborhood were invited to ensure a good spread of the virus. Fortunately, we probably have too few cases of varicella to go around, but the argument for increased social mixing to continually boost immune systems is sound and one more reason not to become a nation of couch potatoes.—a.d.w.