Infant immunization and family size.

Background: To investigate whether a delay in infant immunization is associated with the number of older siblings.

Methods: A cohort analysis of cumulative immunization uptake in 616 children aged 1-4 years recruited for a case-control study of atopic dermatitis in Norwich, UK was performed. The main outcome measures were the age of third pertussis and MMR immunizations.

Atopic dermatitis and the hygiene hypothesis: a case-control study.

Background: The notion that lack of exposure to infection in early life leads to development of atopic disease has come to be known as the hygiene hypothesis. It has arisen from observations of the rapidly rising prevalence of atopic diseases in recent decades and the lower prevalence of atopy with rising birth order. Direct evidence for the hypothesis to date is inconsistent.