Immunogenicity and Safety of ChulaCov19 BNA159 and ChulaCov19 BNA159.2 Vaccines as a Booster Dose in Adults

This is a phase II, randomised open-label trial in which 150 healthy males and non-pregnant females aged 18-64 years, will be recruited from multi-sites in Australia. This is a 2-part study (Part A and Part B). In Part A, the randomisation will be a 2:1 design to receive either ChulaCov19 BNA159 vaccine or Comirnaty Pfizer/BNT vaccine. In Part B, participants will receive only ChulaCov19 BNA159.2 (Bivalent, COMVIGEN) vaccine. Participants in part A and B will be followed up using a combination of an-site and telephone visits for assessment of safety and immunogenicity for 6 months post-vaccination.

Inclusion criteria

• Must be a male or female aged 18 - 64 (inclusive) at the time of enrolment
• Must have completed a primary course of 2 doses of any approved COVID-19 vaccine and 3 months or more have passed since receipt of last booster dose (1 or 2 prior booster doses for a total of 3 or 4 doses) as described in Table 1
• Must be able to communicate effectively with study personnel and considered reliable, willing, and cooperative in terms of compliance with the protocol requirements
• Participants must sign the written informed consent form prior to undertaking any protocol-related procedures
• SARS-CoV-2 rapid antigen test is negative at Day 1 (the day of receiving the study booster dose)
• Does not intend to receive any other authorized/approved COVID-19 vaccine at the time of enrolment and up to 3 months of the study
• Males must be surgically sterile (>30 days since vasectomy with no viable sperm), practice true abstinence or, if engaged in sexual relations with a female of childbearing potential, the participants and their partner must use an acceptable, highly effective, dual contraceptive method* from Screening and for a period of at least 90 days after vaccination
• A female participant is eligible if she is not pregnant, or breastfeeding indicated by one of the following conditions:

• With childbearing potential: she agrees to use an effective contraceptive method or abstinence from at least 4 weeks prior to the study intervention administration until at least 90 days after the study intervention administration, or
• With non-childbearing potential. To be considered of non-childbearing potential, a female must be post-menopausal for at least 1 year or surgically sterile. If the participant is < 1 year post-menopausal, an FSH test may be conducted to establish childbearing potential.
• Participants must be in general good health* based on medical history and physical examination, as determined by the PI at Screening.
• Participants must agree to refrain from donating blood, plasma, ova, sperm, or organs during the whole study.

Exclusion criteria

• History of a systemic hypersensitivity or life-threatening reaction to a vaccine containing any of the same or similar substances.
• History of test-confirmed by PCR or rapid antigen test to SARS-CoV-2 COVID-19 infection within 3 months prior to randomisation.
• Presence of clinically significant medical history*, unstable chronic or acute disease that, in the opinion of the PI, may increase the risk of exposure to the investigational vaccine
• History of having any significant side effects after receipt of any other COVID-19 vaccine eg. endocarditis, pericarditis or myocarditis. History of any severe reactogenic side effects or other medical illness that were thought to be associated with vaccine.
• Presence of an acute illness* or with fever at 38.00 C or more within 72 hours prior to vaccination.
• Bleeding disorders or taking an anticoagulant or anti-platelet agent that may contraindicate for intramuscular injection based on Investigator's judgment
• Inadequate venous access to allow the collection of blood samples.
• Received any prophylactic or therapeutic vaccine, biologic product, device or blood product, within 4 weeks of vaccination or 5 half-lives (whichever is longer) or anticipate doing so in the follow-up period defined for this study. For influenza vaccine, however, can be administered up to 14 days prior to randomization and following Visit 3 (Day 29+3) blood sample collection.
• History of ever had an anaphylaxis reaction to food, medication, or vaccination.
• Participant is immunosuppressed as caused by disease or immunosuppressive therapy or anticipated need to use of any chemotherapy or immunosuppressive agents* within the next 6 months.
• Participation in any of the other investigational trials of vaccines, therapeutic, or medical devices 12 weeks before or during the 6 months of this study.
• Received immunoglobulins and/or any blood or blood products within 3 months before vaccination day or plans to receive any blood or blood products at any time during the study.