LoewenKIDS - Infections and the Development of the Immune System

The goal of the study is to capture the complete history of exposure towards microbial challenges in the first six years of life and to study interactions between different components of microbial exposure as well as effects on the development of immunity. The investigators apply a diary in which parents document symptoms of respiratory and gastrointestinal infections of their child, and collect nasal swabs and stool samples obtained on first day of symptoms. In addition, the investigators collect nasal swabs and stool samples once per year during an asymptomatic period. The investigators intend to collect venous blood from children participating in the study at the age of six years. In a subsample (called intensive subcohort), the investigators collect asymptomatic probes three monthly during the first two years of life and obtain venous blood of the children at the age of one and two years.

The study sample is 782 participants, with 285 participants in the intensive subcohort.

Symptomatic samples will be analyzed by means of multiplex polymerase chain reaction (PCR). In addition, the investigators will assess microbial compositions based on next generation sequencing and apply multiplex panels to study parameters of unspecific humoral immune response. The study will allow to assess homologous and heterologous effects of infections and vaccinations measuring specific humoral immune response. In collaboration with immunologists, immune phenotypes will be studied and functional tests will be conducted.

The investigators will use allergic dermatitis at the age of two as a primary proxy outcome and target asthma at the age of six years as a definitive clinical endpoint.