It is known that the pretreatment with exogenous interferon blocks SARS-CoV-2 infection, but intervention is much more effective if administered prior to infection. In this study the primary aim is to investigate 28-day regime of nasal interferon gama use in healthy participants for COVID-19 and other respiratory infections prevention.

The tissues of the upper respiratory tract: the mucous membrane of the oropharynx, nose, - as well as the lung parenchyma are identified as the main targets of SARS-CoV-2. Previously published data from studies describe that in vitro and in vivo observations SARS-CoV-2 replicates exponentially during the first few days after infection to the peak of the host's antiviral response. It is assumed that it is the violation of the antiviral immunity of the nasal epithelium that may underlie the development of a severe form of the disease. The significance of interferon protection proven in early studies supposes that it can reduce peak viral load and viral reproduction index.

To confirm the efficacy and safety of nasal interferon gama use in healthy participants for COVID-19 and other respiratory infections prevention there is a need of interventional study. Interferon gamma has many years of clinical experience in the prevention and treatment of various viral infections, including coronavirus nature, flu and pneumonia.

After participant enrollment, comprehensive baseline documentation of anamnestic, clinical and allergy data is collected on the same day if possible. For participants who develops acute respiratory symptoms or recieve positive PCR test for SARS-CoV-2, all parameters are collected that may be necessary to assess the type and severity of acute respiratory disease. Furthermore, data is collected that may be suitable for an assessment of the safety profile. In particular, questions are asked about known infection risks, lifestyle, alternative prevention methods, immune competence, rate of acute respiratory infections, the history of symptoms and tests relating to COVID-19, preexisting medication, as well as ethnicity.

On the day of inclusion (day -3-1) routine clinical values, safety-relevant data, WHO scale score, concomitant medication and anamnesis, as well as study criteria analysis are documented.

On the day 0 (randomization visit) and at termination visit (up to 90 days) repeated routine clinical values, safety-relevant data, WHO scale score, and concomitant medication are collected. If the patient falls ill, the necessary disease information is documented. If the patient dies, the date and cause of death are documented.

On days 24-30 after randomization, a follow-up call takes place with particular attention to the health-related events such as respiratory diseases or other changes in health and vital status and drug compliance. If the participant cannot be reached for the follow-up call, the including study center will attempt to reach the participant, otherwise exclude the participant.

A nasopharynx swab is obtained on days 0 to exclude asymptomatic patients before the randomisation. If possible, sputum is obtained for termination visit and during the acute respiratory symproms manifestation to confirm COVID-19.

Inclusion Criteria:

• Volunteers of both sexes over 18 years of age.
• Obtaining written informed consent.
• Ability and consent to participate in this research.
• Absence of symptoms of respiratory infection.
• A negative result of a PCR study for the presence of RNA SARS-CoV-2 according to biomaterial obtained by nasopharyngeal smear.

Exclusion Criteria:

• Any other concomitant diseases or conditions, which, in the opinion of the research doctor, may distort research results, restrict the rights of a volunteer or put him/her at greater risk.
• Contraindications to the use of the investigated medicinal product.
• Individual intolerance to the ingredients included in the composition of the investigational medicinal product.
• Pregnancy or breastfeeding.
• Doubtful result of a PCR test for the presence of RNA SARS-CoV-2 in the biomaterial obtained by nasopharyngeal smear.
• Participation in a clinical trial using study therapy within 30 days prior to enrollment in this study.
• Disagreement to follow in the research reliable contraceptive measures (abstinence; or a combination of 2 different methods: for example, barrier and spermicides, or barrier and intrauterine device, or barrier and hormonal, etc.) - for participants with saved reproductive potential.