Safety and Immunogenicity of a Novel Conjugate Vaccine Against Salmonella Typhi and Salmonella Paratyphi A in Healthy Adults

Inclusion Criteria

• Participants who, in the opinion of the Investigator, can and will comply with the requirements of the Protocol (e.g., completion of the diary cards, return for follow-up visits).
• Written informed consent obtained from the participant prior to performance of any study specific procedure.
• Healthy participants as established by medical history, clinical examination, and screening laboratory investigations.
• Participant satisfying screening requirements.
• Participant seronegative for human immunodeficiency virus, hepatitis B, and hepatitis C at Screening.
• A male or female participant between, and including, 18 and 50 years of age at the time of the first study intervention administration.
• Female participants of non-childbearing potential may be enrolled in the study. Non-childbearing potential is defined as pre-menarche, current bilateral tubal ligation or occlusion, hysterectomy, bilateral ovariectomy or post-menopause.
• Female participants of childbearing potential may be enrolled in the study if the participant:
• has practiced adequate contraception for 1 month prior to study intervention administration, and
• has a negative pregnancy test on the day of study intervention administration, and
• has agreed to continue adequate contraception during the entire treatment period and for 1 month after completion of the study intervention administration series.

Exclusion Criteria

Medical conditions

• Progressive, unstable or uncontrolled clinical conditions.
• History of any reaction or hypersensitivity likely to be exacerbated by any component of the vaccine.
• Hypersensitivity, including allergy, to medicinal products or medical equipment whose use is foreseen in this study.
• Clinical conditions representing a contraindication to intramuscular vaccination and blood draws.
• Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination (no laboratory testing required).
• Any behavioural or cognitive impairment or psychiatric disease that, in the opinion of the Investigator, may interfere with the participant's ability to participate in the study.
• Acute* or chronic illness, clinically significant pulmonary, cardiovascular, hepatic, or renal functional abnormality, as determined by physical examination or laboratory screening tests.

*Participants with a minor illness (such as mild diarrhoea or mild upper respiratory infection) without fever may be enrolled at the discretion of the Investigator.

• Any clinically significant* haematological and/or biochemical laboratory abnormality.

*The Investigator should use his/her clinical judgement to decide which abnormalities are clinically significant.

• Confirmed positive COVID-19 test during the period starting 14 days before the first administration of study vaccines (Day -14 to Day 1).
• Any other clinical condition that, in the opinion of the Investigator, might pose additional risk to the participant due to participation in the study.
• Confirmed or suspected autoimmune diseases (e.g., vitiligo, autoimmune thyroiditis).

Prior/Concomitant therapy

• Previous administration of any type of Typhoid vaccine (Ty21a, Vi-PS, or Typhoid conjugate vaccine).
• Use of any investigational or non-registered product (drug, vaccine, or medical device) other than the study interventions during the period starting 30 days before the first administration of study vaccines (Day -30 to Day 1), or planned use during the study period.
• A vaccine not foreseen by the study protocol administered during the period starting at -14 days before the first dose (-21 days in the case of live vaccines) and ending 28 days after the last dose of study intervention administration*, with the exception of flu and COVID-19 vaccines, administered during the period starting at 7 days before and 7 days after each dose (14 days before and 14 days after in case of live vaccines).

*In case emergency mass vaccination for an un