The effect of probiotics on respiratory and gastrointestinal infections in children attending daycare

Background: Respiratory and gastrointestinal infections are common during childhood, especially in young infants < 2 years of age. Although these common infections are rarely fatal inhigh-income countries as Denmark, they are a source of significant morbidity burden to thechildren and their families, and lead to a substantial economic burden on society. Childrenattending daycare have an increased risk of infections, mainly due to an increased exposure topathogens through social interaction between children, and due to a not yet fully developedimmune system. Strategies to prevent infections in daycare settings are of great importance in acountry like Denmark, where 90 % of children are cared for outside the home in daycare facilitiesby the age of 2 years. Probiotics, defined as live microorganisms that when administered inadequate amounts, confer a health benefit on the host have been suggested in prevention ofrespiratory and gastrointestinal infections in children. Objective: The main objective of this PhD thesis was to examine the effect of probiotics inreducing absence from daycare due to respiratory and gastrointestinal infections in Danish infantsduring their first months in a daycare setting, and to explore potential factors modifying the riskof infections. Further, the current evidence on the use of probiotics in prevention of respiratoryinfections in children attending daycare was systematically reviewed. Methods: Paper I reports on a randomized, placebo-controlled trial investigating the effect ofprobiotics on absence from daycare due to respiratory and gastrointestinal infections in Danishinfants (The ProbiComp study). A total of 290 infants were randomly allocated to receive placeboor a combination of Bifidobacterium animalis subsp. lactis BB-12 and Lactobacillus rhamnosusGG in a dose of 109 colony-forming units per day of each for a 6-month intervention period. Absence from daycare, symptoms of illness, and doctors visits were registered by the parents