This study evaluates the performance of ColdZyme® mouth spray on prevention of common cold symptoms on experimentally induced rhinovirus upper respiratory tract infection in healthy volunteers. Half of participants will receive ColdZyme® mouth spray while the other half will receive placebo.

88 subjects will be inoculated with rhinovirus 16 via the nasal route. The subjects will be randomized 1:1 to ColdZyme® or placebo. Treatment (6 doses per day) will be applied for 11 days from the day of inoculation. The subjects will visit the investigational clinic on 6 occasions. During these visits the subjects will leave nasal (lavage) and pharyngeal (swab) samples for quantification of virus replication. All subjects will have a diary for scoring of cold symptoms.

Inclusion Criteria:

• Healthy male or female subjects between 16-70 years. The investigator judges the definition of healthy by detailed medical history and physical examination.
• Females of childbearing potential: shall use reliable method of birth control. Reliable methods are hormonal contraceptives (combination pills, injections or implants), intrauterine device, condom or declared absence of sexual contact. Post-menopausal woman is defined as absence of menstrual discharge for at least two years.
• Signed informed consent form prior to any study-related procedures.
• Willingness and ability to adhere to the prohibitions and restrictions specified in this protocol.
• Perceived to have had at least one cold per year

Exclusion Criteria:

• Smoker, during the last 12 months
• Any cold symptom within the last month such as sore throat, sneezing, rhinorrhoea, malaise, nasal obstruction or cough.
• Presence (at screening) of serum rhinovirus 16 neutralising antibody titers at greater than or equal to one in two dilution.
• Active allergic rhinitis, asthma or chronic obstructive pulmonary disease during study period.
• Nasal disease, e.g. nasal polyposis, significant septal deviation, chronic rhinosinusitis, etc.
• Females: Pregnant, breast-feeding or intentions to become pregnant during the study.
• Evidence or history of drug or alcohol abuse.
• Use of any prescribed or non-prescribed medication (except for contraceptives, paracetamol and ibuprofen) within 2 weeks prior to the first administration of investigational product.
• Use of any over the counter cold prophylaxis products such as ColdZyme®, C-vitamins, zinc or Echinacea within 1 month prior to the first administration of investigational product.
• Participation in other clinical trial with medical investigational product within 60 days prior to the first administration of investigational product.
• Hypersensitivity/allergy to any of the device ingredients
• Individuals with close contact to at risk patient group:
• infants (less than 6 months);
• the extremely elderly or infirm;
• pregnant women;
• patients with severe lung disease (asthma/cystic fibrosis (CF)/COPD);
• patients with immunosuppression.