2.1. Recruitment, Blinding and Randomization
allergy
RECRUITMENT, ALLERGY, POLAND
All trial subjects were pre-school children (3–7 years of age; mean, 4.3 ± 1.21 years; male to female ratio—1:0.8) attending one of the two large (over 300 pupils) public kindergartens facilities in Szczecin, Poland. Trial participants were invited through the advertisements posted in these facilities. The only exclusion criterion was an allergy to cow’s milk. The general health status of all participants was considered to be good, suitable for participating in kindergarten activities.Trial administration, which included the enrolment process, collection of formal consent forms, blinding and randomization of participants and database maintenance, was performed by a dedicated person—the administrator. He was also the only person who contacted participants via email and provided them with links to the online survey forms (both the initial and daily/weekly surveys). The polls the participants responded to were based on the EU Survey system, an official online survey management tool provided for free by the European Commission [After receiving the approval by the Ethical Committee of the Pomeranian Medical University in Szczecin, the study also obtained the acceptance from the managements of both facilities where the children were enrolled. The recruitment of participants began with a series of meetings where parents and guardians were provided with a comprehensive explanation of the study principles in both verbal and written form. They were given the opportunity to ask any questions regarding their child’s participation in the trial.We obtained formal consent forms from the parents and guardians of 89 participants. Upon recruitment, the administrator immediately assigned a trial ID number to each participant, by which they were referred to for the rest of the trial. This way, the identity of all children remained anonymous to all investigators (including cooperating kindergartens managements), as well as other participants (parents and guardians), until the completion of data analysis. Upon blinding, the random assignment to tested groups was performed with the MS Excel Random Sort tool. Out of 89 participants recruited, we were able to form the colostrum (COL) group consisting of 45 children and the placebo (PBO) group consisting of 44 children.