Can immunization affect the development of allergy?

A changing pattern of infections may be of importance for the increase in p revalence of asthma and other allergic diseases in developed countries duri ng recent decades. The clear inverse relation between number of siblings an d atopy observed in several studies may be related to a protective role of infections, although specific information is inconclusive. A recent study s howed that positive tuberculin responses in schoolchildren correlated with a lower prevalence of atopic disorders, but other studies did not find a re lation between BCG vaccination and allergic disease or sensitization. Trans ient production of IgE antibodies to pertussis toxin has been demonstrated after pertussis immunization; however: randomized clinical trials involving both whole cell and acellular pertussis vaccines have failed to show any e nhancement of atopic manifestations in children. Epidemiologic investigatio ns indicate that viral infections may either promote (RSV) or inhibit (hepa titis A, measles) atopy, although data are scarce. In conclusion, the evide nce is limited regarding a direct role of vaccinations for development of a topic manifestations, but speaks against a major effect of some types of va ccinations. On the other hand, since some infections may offer protection i n relation to allergy, vaccination could result in an increased risk.