- antibiotic use at baseline and during the study - vaccinated against sars-cov-2 at start of the study (both for index patients and household members that participate) - pregnant women - history of use of probiotic supplements in the past two weeks - current diagnosis of cancer or immunosuppressive therapy within the past 6 months - acute and chronic infectious and inflammatory upper airway diseases (eg acute / chronic rhinosinusitis) - clinically significant bleeding disorder - any other medical condition that, in the principal investigator's opinion, warrants exclusion from the trial

- antibiotic use at baseline and during the study - vaccinated against sars-cov-2 at start of the study (both for index patients and household members that participate) - pregnant women - history of use of probiotic supplements in the past two weeks - current diagnosis of cancer or immunosuppressive therapy within the past 6 months - acute and chronic infectious and inflammatory upper airway diseases (eg acute / chronic rhinosinusitis) - clinically significant bleeding disorder - any other medical condition that, in the principal investigator's opinion, warrants exclusion from the trial