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 therequirements of the Protocol (e.g., completion of the diary cards, return forfollow-up visits).

• Written informed consent obtained from the participant prior to performance of anystudy specific procedure.

• Healthy participants as established by medical history, clinical examination, andscreening laboratory investigations.

• Participant satisfying screening requirements.

• Participant seronegative for human immunodeficiency virus, hepatitis B, andhepatitis C at Screening.

• A male or female participant between, and including, 18 and 50 years of age at thetime 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 tuballigation or occlusion, hysterectomy, bilateral ovariectomy or post-menopause.

• Female participants of childbearing potential may be enrolled in the study if theparticipant:

• has practiced adequate contraception for 1 month prior to study interventionadministration, and

• has a negative pregnancy test on the day of study intervention administration,and

• has agreed to continue adequate contraception during the entire treatmentperiod and for 1 month after completion of the study interventionadministration series.

Exclusion Criteria:

Medical conditions

• Progressive, unstable or uncontrolled clinical conditions.

• History of any reaction or hypersensitivity likely to be exacerbated by anycomponent of the vaccine.

• Hypersensitivity, including allergy, to medicinal products or medical equipmentwhose use is foreseen in this study.

• Clinical conditions representing a contraindication to intramuscular vaccination andblood draws.

• Any confirmed or suspected immunosuppressive or immunodeficient condition, based onmedical history and physical examination (no laboratory testing required).

• Any behavioural or cognitive impairment or psychiatric disease that, in the opinionof the Investigator, may interfere with the participant's ability to participate inthe study.

• Acute* or chronic illness, clinically significant pulmonary, cardiovascular,hepatic, or renal functional abnormality, as determined by physical examination orlaboratory screening tests.

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

• Any clinically significant* haematological and/or biochemical laboratoryabnormality.

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

• Confirmed positive COVID-19 test during the period starting 14 days before the firstadministration of study vaccines (Day -14 to Day 1).

• Any other clinical condition that, in the opinion of the Investigator, might poseadditional 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 Typhoidconjugate vaccine).

• Use of any investigational or non-registered product (drug, vaccine, or medicaldevice) other than the study interventions during the period starting 30 days beforethe first administration of study vaccines (Day -30 to Day 1), or planned use duringthe study period.

• A vaccine not foreseen by the study protocol administered during the period startingat -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 theexception of flu and COVID-19 vaccines, administered during the period starting at 7days before and 7 days after each dose (14 days before and 14 days after in case oflive vaccines).

*In case emergency mass vaccination for an unforeseen public health threat (e.g., apandemic) is recommended and/or organised by public health authorities outside theroutine immunisation programme, the time period described above can be reduced if,necessary for that vaccine, provided it is used according to the local governmentalrecommendations and that the Sponsor is notified accordingly. When regulationsallow, the recommended time intervals for administration of these vaccines are atleast 7 days before or 7 days after (at least 14 days before or 14 days after incase of live vaccines) each dose of study intervention administration.

• Administration of long-acting immune-modifying drugs at any time during the studyperiod (e.g., infliximab).

• Administration of immunoglobulins and/or any blood products or plasma derivativesduring the period starting 3 months before the administration of the first dose ofstudy intervention or planned administration during the study period.

• Chronic administration (defined as more than 14 days in total) of immunosuppressantsor other immune-modifying drugs during the period starting 3 months prior to thefirst study intervention dose. For corticosteroids, this will mean prednisoneequivalent ≥20 mg/day for adult participants. Inhaled and topical steroids areallowed.

Prior/Concurrent clinical study experience • Concurrently participating in another clinical study, at any time during the study period, in which the participant has been or will be exposed to an investigational or a non-investigational vaccine/product (drug/invasive medical device).

Other exclusions

• History of travel to countries of Asia that are considered endemic* for entericfever in the last 3 years.

*this also includes travel during study duration.

• Pregnant or lactating female.

• Female participants planning to become pregnant or planning to discontinuecontraceptive precautions.

• History of or current chronic alcohol consumption and/or drug abuse.

• Any study personnel or immediate dependents, family, or household member.