Study on Immunogenicity, Reactogenicity and Safety of the VACΔ6 Vaccine in Volunteers Aged 18-60 Years

The Aim:

Study immunogenicity, confirm the safety and tolerability of different schedules of vaccination with "live cell-based vaccine against smallpox and other orthopoxvirus infections (VAC∆6 vaccine) based on vaccinia virus" using a complex of clinical and laboratory-instrumental techniques.

The research tasks are to:

1. To study the immunological activity of a single VAC∆6 vaccine dose of 1x10⁷ plaque-forming units (PFU).
2. To study the immunological activity of two VAC∆6 vaccine doses (given 28 days apart) of 1x10⁶ PFU.
3. Assess the safety of different VAC∆6 vaccination schedules using a set of clinical and laboratory-instrumental techniques (thermometry, measurement of blood pressure, heart and lung auscultation, ECG, common blood and urine tests, biochemical, immunological and virological studies).
4. Assess the reactogenicity of different VAC∆6 vaccination schedules (number of local and systemic reactions, the percentage of those vaccinated with systemic and local reactions of various severity degrees).
5. To identify VAC∆6 vaccine-associated adverse events.
6. Study cell-mediated immunity induced by different VAC∆6 vaccination schedules.
7. Determine the presence of the virus in specific skin formations (crusts, pustules), saliva, blood and urine.
8. Evaluate the protective efficacy of one and two doses of the studied VAC∆6 vaccine.

This is a Double-blind, Comparative, Randomized, Placebo-controlled Study on Immunogenicity, Reactogenicity and Safety of Live Cell-Based Vaccine Against Smallpox and Other Orthopoxvirus Infections (VAC∆6 Vaccine) Based on Vaccinia Virus in 18-60-year-old Volunteers.

The study included 334 healthy volunteers of both sexes aged 18-60 years who met the inclusion criteria and had no exclusion criteria.

The study was carried out in two stages:

The first stage is an open comparative study of the safety, reactogenicity, immunological activity and protective efficacy of VAC∆6 vaccine in parallel groups of 30 volunteers aged 18 to 60 who met the inclusion criteria. Volunteers were divided into two groups:

* Group 1: 15 volunteers who received a single intradermal VAC∆6 dose of 1x10⁷ PFU. Live smallpox vaccine was administered by scarification 2 months after the vaccination.
* Group 2: 15 volunteers who received two intradermal VAC∆6 doses of 1x10⁶ PFU (given 28 days apart). Live smallpox vaccine was administered by scarification one month after the full vaccination series.

The second stage is a Double-blind, Comparative, Randomized, Placebo-controlled study on Immunogenicity, Reactogenicity, and Safety of the VAC∆6 Vaccine in Parallel Groups. Randomization was carried out using the envelope method. The sealed opaque envelopes included in the Investigator's File were distributed to the clinical sites in the required quantity prior to the start of the study.

Substances were submitted for testing in encrypted form. The encryption technique was chosen and implemented by the sponsor - FBRI SRC VB "Vector", Rospotrebnadzor. Decryption was carried out after study report submission to the Federal Budgetary Research Institution, State Research Center of Virology and Biotechnology "Vector", Rospotrebnadzor.

A total of 304 volunteers aged 18-60 took part in the second stage of the clinical study, of which 158 were men and 146 were women, who met the inclusion criteria and had no exclusion criteria. The volunteers were assigned to study sites as follows:

1. FGBUZ MSCH-163, FMBA Russia - 272 volunteers randomized into four groups:

   * Group 3: 76 volunteers who received two intradermal VAC∆6 doses of 10⁶ PFU/0.2 ml (given 28 days apart);
   * Group 4: 76 volunteers who received two intradermal placebo doses of 0.2 ml (given 28 days apart);
   * Group 5: 60 volunteers who received a single intradermal VAC∆6 dose of 10⁷ PFU/0.2 ml;
   * Group 6: 60 volunteers who received a single intradermal placebo dose of 0.2 ml.
2. State Budgetary Health Institution of the Novosibirsk Region "Municipal Infectious Disease Clinical Hospital No. 1" - 32 volunteers randomized into two groups:

   * Group 7: 16 volunteers who received a single intradermal VAC∆6 dose of 10⁷ PFU/0.2 ml;
   * Group 8: 16 volunteers who received a single intradermal placebo dose of 0.2 ml.

     * Before applying for a state license to the Ministry of the Russian Federation on May 4, 2022, the VACΔ6 vaccine was renamed to OrthopoxVac.

Eligibility Criteria:
Inclusion Criteria:

1. Signed and dated informed consent of a volunteer to participate in a clinical trial obtained prior to any of the study procedures.
2. A verified diagnosis of "healthy" according to standard clinical, laboratory and instrumental methods of examination.
3. Age from 18 to 60 inclusive.
4. Body mass index from 18.5 to 30 kg/m3.
5. Ability to attend all scheduled visits and all scheduled procedures and examinations.
6. Consent of volunteers to use effective methods of contraception throughout the study, including the period of observation for possible post-vaccination reactions.

Exclusion Criteria:

1. Hypersensitivity to any component of the product, allergy to vaccine components.
2. Pregnancy or breastfeeding.
3. The military.
4. Persons in custody in detention facilities and those serving sentences in correctional facilities.
5. Children under 18.
6. Acute infectious or non-infectious diseases, exacerbation of chronic diseases less than 4 weeks prior to the study.
7. Tuberculosis (pulmonary and extrapulmonary).
8. Skin diseases: a) common dermatoses (pemphigus, psoriasis, eczema, atopic dermatitis), including the history of dermatoses; other acute and chronic diseases or impaired skin cover (burns, impetigo, herpes, herpes zoster/chicken pox, pustular diseases).
9. Immunosuppressive conditions: congenital or acquired immunodeficiency syndrome (including HIV infection), leukemia, malignant neoplasms, organ transplantation, cellular and humoral immunodeficiencies.
10. Immunosuppressive therapy: treatment with antimetabolites, high doses of corticosteroids for 14 days or more, radio and x-ray therapy, etc.
11. Regular medication intake less than 2 weeks before the start of the study.
12. Taking immunoglobulin drugs or blood products within the last 3 months before the start of the study.
13. Donation (450 ml of blood or plasma or more) less than 2 months before the start of the study.
14. Cardiovascular diseases: decompensated heart defects, subacute bacterial endocarditis, myocarditis, pericarditis, stage 2-3 hypertension, angina pectoris, myocardial infarction; other forms of pathology: stage 1 hypertension, well-controlled heart defects, angina pectoris (mild forms).
15. Diseases of the kidneys and urinary tract: diffuse glomerulonephritis, congenital nephropathy, chronic renal failure, pyelonephritis, toxic nephropathy (transient).
16. Diseases of the digestive system: cirrhosis of the liver, chronic hepatitis, hepatocerebral dystrophy, acute and chronic pancreatitis, diseases of the biliary tract, gastric ulcer and duodenal ulcer, ulcerative colitis.
17. Diseases of the endocrine system: diabetes mellitus, severe forms of thyrotoxicosis and adrenal insufficiency or dysfunction, thymomegaly, congenital enzymopathy.
18. Systemic connective tissue diseases: systemic lupus erythematosus, discoid lupus, rheumatism, rheumatoid arthritis, systemic vasculitis, systemic scleroderma.
19. Blood diseases: leukemia, Hodgkin's disease, aplastic anemia, hemophilia, Werlhof's disease; hemolytic conditions; deficiency anemia.
20. Allergic diseases: bronchial asthma; asthmatic bronchitis, asthmatic syndrome (associated with a respiratory infection); severe anaphylactic reactions (shock, angioedema of the larynx, etc.) to a variety of food, drug and other allergens; allergic reactions to individual allergens (various rashes, clinical disorders, etc.).
21. Diseases of the ear, throat, nose: chronic tonsillitis and adenoiditis requiring surgical treatment; chronic otitis.
22. Surgery within the previous 2 months.
23. Participation in other clinical trials less than 3 months prior to study enrollment.
24. Persons with alcohol, drug or drug addiction. Drinking more than 10 units of alcohol per week (1 unit of alcohol is equivalent to ½ liter of beer, 200 ml of wine or 50 ml of alcohol) or a history of alcoholism, drug addiction, drug abuse.
25. Mental illness and neurasthenia.
26. Previous treatment with human immunoglobulin preparations, if less than 6 months have passed since the treatment.
27. Failure to meet inclusion criteria.
28. Vaccination with any vaccine less than 2 months prior to study entry.
29. Premenopausal women (last menstrual period ≤ 1 year prior to signing the informed consent) who are not surgically sterile.
30. Women who have reproductive potential and do not use or plan to use approved birth control products throughout the study and do not agree to urine pregnancy testing while participating in the study. Acceptable birth control methods include extrauterine devices, oral, implanted, or injectable contraceptives.
31. Nervous and mental diseases: injuries of the central nervous system (CNS) with residual effects, encephalitis and encephalomyelitis (including post-vaccination), meningitis, polyradiculoneuritis (including the history of polyradiculoneuritis), epilepsy, decompensated or subcompensated hydrocephalus, demyelinating and degenerative lesions of the nervous system (muscle degeneration, etc.), stroke; compensated hydrocephalus, Down's disease, Little's disease, CNS trauma without residual effects, history of febrile convulsions, mental illness.
32. Positive analysis for HIV, viral hepatitis B and C, lues.
33. Other сoncomitant diseases that, in the opinion of the investigator, may interfere with the aims of the study.
34. Serious post-vaccination reactions/complications associated with any previous vaccination.