...Or childhood vaccinations?

Several studies have shown that the incidence of allergies and asthma tends to rise in countries where childhood immunization rates are high. This has prompted some researchers to suggest that certain infections may trigger immune changes that somehow protect children from developing allergies and asthma later. Preliminary studies have shown a protective effect of, for example, measles and infections with some intestinal parasites. Indeed, this observation may explain the findings of a new study involving 867 school-age children in Japan. Taro Shirakawa of Churchill Hospital in Oxford, England, and his coworkers compared a history of asthma and other allergic conditions in these children with whether the youngsters had been vaccinated against tuberculosis. They also surveyed if and when a child tested positive on a skin test for the dis- ease.

In the Jan. 3 Science, they report that children who tested positive for tuberculosis-probably as a response to the vaccine-were only one-third as likely to have allergies as those who tested negative. Similarly, children testing positive were only one-half to one-third as likely to exhibit asthma symptoms.

In an accompanying editorial, William O.C.M. Cookson and Miriam F. Moffatt of the University of Oxford speculate "that the decline in childhood tuberculosis infection in Japan is causal in the recent asthma epidemic." Since tuber-culosis triggers a reaction called delayed hypersensitivity in the immune system, the pair suggests that a vaccine designed to elicit this response might prove effective in fighting allergy and asthma in children.