Lead Sponsor

Leiden University Medical Center

Collaborators

Age

1 - 5 years

Sex

ALL

Healthy Volunteers

No

•Written informed consent obtained from all legal representatives, for example both parents.
•Child aged 1-5 years of age attending day care, peuterspeelzaal or school at least 2 (half) days a week.
•Parents ability and willingness to adhere to protocol-specified procedures, including availability of a freezer at home to store samples. This does not include donation of saliva by parents themselves, which is related to a secondary endpoint.

•History of respiratory tract infections requiring hospitalization
•Current use of antibiotics, or antibiotics use in past four weeks
•Use of immune-altering medication (such as steroids, including inhaled corticosteroid)
•No history of severe concomitant disease (severe congenital heart disease, bronchopulmonary dysplasia, prematurity \<32 weeks, cystic fibrosis, sickle cell disease, congenital or acquired immunodeficiency disorders, cardiovascular disease, neuromuscular disorders, oncology patients or major congenital anomalies)