Participants
malignancy, allergic diseases
MAY, DISEASES, RECRUITMENT
Participants were enrolled through a website between May and July 2021. Following declaration of willingness to participate in the trial and an initial online screening, potentially eligible volunteers were invited to attend the trial unit for further psychological, clinical, and laboratory evaluations and to sign a written informed consent. At the psychological assessment session, the participants’ mental capability to give consent was assessed before proceeding with the rest of the trial. Major inclusion criteria were age between 18 and 70 with negative serology (anti-nucleocapsid antibody) and no clinical history for COVID-19, and negative RT-PCR test at the time of recruitment. Major exclusion criteria were pregnancy, breastfeeding, history of allergic diseases and reactions, having any active uncontrolled diseases, malignancy, and close contact with a person with confirmed COVID-19 for a maximum of 2 weeks before the screening day. A detailed description of eligibility criteria has been presented in the Study protocol [Additional file 