An interventional study of Probiotic Formula and Matching placebo in Upper Respiratory Tract Infections, sponsored by Harokopio University. Recruiting at 1 site in Greece. Open to participants aged 18 Years to 65 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-11-02.
Sponsored by Harokopio University · Not applicable, Interventional, and Prevention
This randomized, double-blind, placebo-controlled clinical trial in generally healthy adults aged 18-65 years will compare the incidence of upper respiratory tract infections (URTIs) over 16 weeks between probiotic supplement and placebo.
This study will evaluate whether a daily probiotic formula can reduce the occurrence of upper respiratory tract infections (URTIs) in generally healthy men and women aged 18-65 years. A total of 140 participants will be randomly assigned to receive either the probiotic formula or a matching placebo once daily for 12 weeks, followed by a 4-week period without study product.Participants will complete daily mobile-based monitoring for cold and upper respiratory symptoms throughout the 16-week study. The main outcome is the number of clinically confirmed URTI episodes experienced by each participant. The study will also assess symptom severity and duration, medication and antibiotic use, healthcare utilization, days missed from work or study, quality of life, gastrointestinal symptoms, safety and tolerability, as well as changes in oral microbiota and inflammatory biomarkers.
751 studies on the registry are indexed under Respiratory Tract Infections; 114 are open to participants now.
This study's planned enrollment of 140 is below the median of 200 across 540 interventional studies indexed under Respiratory Tract Infections.
Browse Respiratory Tract Infections studies →Harokopio University is the lead sponsor of 66 studies on the registry; 9 are open to participants now.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Excipients
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will receive the probiotic formula, one sachet once daily for 12 weeks.
Dietary Supplement: Probiotic Formula
Participants will receive a matching placebo sachet, one sachet once daily for 12 weeks.
Dietary Supplement: Matching placebo
The probiotic formula provides a total of 1.25 × 10⁹ CFU of live probiotic microorganisms per sachet. Participants will take one sachet once daily at night for 12 consecutive weeks.
Matching sachet formulation containing no probiotic microorganisms. Participants will take one sachet once daily at night for 12 consecutive weeks.
Number of clinically confirmed upper respiratory tract infection (URTI) episodes per participant
The number of clinically confirmed URTI episodes experienced by each participant during the study.
Time frame: 16 weeks (Week 0 to Week 16)
Proportion of participants experiencing clinically confirmed URTI episodes
Proportion of participants experiencing at least 1, at least 2, and at least 3 clinically confirmed URTI episodes during the study period.
Time frame: 16 weeks (Week 0 to Week 16)
URTI episode duration and timing
Duration of individual clinically confirmed URTI episodes, cumulative symptomatic days, URTI-free time, and time to first clinically confirmed URTI episode.
Time frame: 16 weeks (Week 0 to Week 16)
Predominant symptom-based URTI clinical presentation
Clinical characteristics and treatment outcomes of clinician-confirmed URTI episodes classified according to the prespecified study-specific symptom-domain classification.
Time frame: 16 weeks (Week 0 to Week 16)
Sore-throat outcomes during clinically confirmed URTI episodes
Number of clinically confirmed URTI episodes involving sore throat, duration and severity.
Time frame: 16 weeks (Week 0 to Week 16)
Medication and healthcare utilisation related to URTI episodes
Use of symptomatic medications, prescribed antibiotics, and healthcare services related to clinically confirmed URTI episodes.
Time frame: 16 weeks (Week 0 to Week 16)
Days absent from work or study due to URTI illness
Number of days absent from work or study because of clinically confirmed URTI illness during the study period.
Time frame: 16 weeks (Week 0 to Week 16)
Health-related quality of life
Health-related quality of life assessed using the EQ-5D-5L at prespecified study timepoints.
Time frame: Baseline (Week 0), Week 12, and Week 16
Gastrointestinal symptoms
Gastrointestinal symptom burden assessed using the 15-item Gastrointestinal Symptom Rating Scale (GSRS).
Time frame: Baseline (Week 0), Week 12, and Week 16
Change in oral microbiota composition
Changes in oral microbiota composition and prespecified microbiota features assessed using 16S rRNA gene sequencing of saliva samples collected at baseline and Week 12.
Time frame: Baseline (Week 0) to Week 12
Change in systemic inflammatory biomarkers
Changes in systemic inflammatory biomarkers, including high-sensitivity C-reactive protein (hs-CRP) and interleukin-6 (IL-6), assessed using fasting blood samples collected at baseline and Week 12.
Time frame: Baseline (Week 0) to Week 12
Adherence to the study intervention
Adherence to the allocated study product assessed during the 12-week intervention using electronic adherence records and corroborated by returned sachet counts at Week 12.
Time frame: 12 weeks (Week 0 to Week 12)
Safety and tolerability
Frequency, nature, severity, seriousness, and relationship to the study product of reported adverse events, together with study-product discontinuations attributable to adverse events.
Time frame: 16 weeks (Week 0 to Week 16)
Dietary intake and physical activity
Dietary intake and prespecified measures of physical activity, including changes where applicable, assessed over the study period.
Time frame: Baseline (Week 0), Week 12, and Week 16
Plan to share: No
No publications or documents are linked to this record.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Respiratory Tract Infections →
Harokopio University