ZyVac-TCV Bangladesh Study

This will be a phase III effectiveness study of the typhoid conjugate vaccine (Vi-TCV) (ZyVac® TCV). The study will be conducted in a closed cohort population of children aged 6 months to 15 years residing in a selected geographical catchment area in Dhaka, Bangladesh using a test-negative design (TND). The TND is a particular type of case-control study including controls who present themselves with similar signs and symptoms (to those of the cases) in the same healthcare facilities. Individuals with the disease of interest are tested with a laboratory assay where test-positive and test-negative individuals are considered cases and controls, respectively.

Hypothesis:

The typhoid Vi-polysaccharide conjugate vaccine will be effective in preventing typhoid fever among Bangladeshi children.

Specific Objectives

Primary objective:

To evaluate the effectiveness of typhoid conjugate vaccine (TCV) against blood culture-confirmed typhoid fever using the test-negative design

Secondary objective:

To evaluate the effectiveness of typhoid conjugate vaccine (TCV) against blood culture-confirmed typhoid fever stratified by age groups (6 months to \<2 years, 2 to 4 years, 5 to 15 years) To evaluate the effectiveness of typhoid conjugate vaccine (TCV) against blood culture-confirmed typhoid fever stratified by the period of follow-up (first and second six months) after vaccination To determine the immunogenicity of TCV in a subset of participants, stratified by age groups (6 months to \<2 years, 2 to 4 years, 5 to 15 years)

Study area The study will be conducted in wards 5, 6, 7, 48, 49, 50, 63, 71, and 72 of Dhaka South City Corporation, covering an area of \~10.33 km2. No TCV campaigns have been conducted in this area. According to the Population and Housing Census 2022, the total population within the selected geographical catchment area is \~465,000 with households of \~122,000. The proportion of males is 54 percent and the average household size is \~3.8 people. Assuming \~20% of the population is from the 6-month to 15-year age group, the expected number of age-eligible children is \~92,000.

Baseline mapping A map of the study area will be created based on open-source georeferenced satellite images (source: Esri, Maxar, Earthstar Geographics, and the geographical information system (GIS) user community). The satellite image of the study area will be printed by separating it into several small pieces and provided to the field team for data collection. In this process field team will visit the entire area according to the map and draw the structure/building, road, and other salient geographic features in the printed images. A unique geographical information system (GIS) identification number will be assigned for all the buildings/structures, and submitted to the GIS team to develop the digital vector data (point, line, and polygon feature). The digital data of structure/building (polygon feature) centroid x and y coordinates will be used to represent real-world coordinate values or global positioning system (GPS) values.

Baseline listing All households in the study area will be assigned a unique identification number and all household members will be enumerated. Information about the age-eligible children including name, age, sex, date of birth, and parent's name will be obtained. In addition, the name of the HH head, address, and cell phone number of HHs will be collected. The previously assigned GIS ID will be incorporated into the baseline listing form and the newly identified structure will be updated in the GIS database. We will take photos of birth certificates or national immunization cards to confirm the age of participants if available. Verbal consent will be provided by either the head of the household or a key informant.

Participant card for potentially eligible children for vaccination After preparing the baseline list, we will identify the age-eligible (6 months to 15 years) participants. Then we will prepare participant cards for all eligible children which will be provided before the vaccination. There will be a unique identification number on the participant card which will be used during vaccination. A master list of potential eligible participants will be prepared.

Vaccination

Temporary exclusion criteria for vaccination:

Participants will be temporarily excluded from being vaccinated if, at the point of vaccination, any of the following apply:

Receipt of any other vaccines in the last 30 days Current temperature of at least 38oC or reported fever within 24 hours prior to vaccination Use of antipyretics within 4 hours prior to vaccination Unmarried girls between the ages of ≥12 to 15 years old whose first day of their last menstrual period (LMP) is more than 28 days ago or who do not know the date they last menstruated upon presentation

If these apply, the participant will be temporarily excluded from vaccination until the temporary exclusion criteria no longer apply. Please note, for children with fever above 38oC this must be a minimum of 48 hours after the fever has resolved. Unmarried girls between the ages of ≥12 to 15 years whose first day of their LMP is more than 28 days or who do not know the date they last menstruated upon presentation will be asked to return after starting their next menstruation for vaccination. A re-assessment will be conducted to ensure these temporary exclusion criteria no longer exist.

Verification of the potentially eligible children All the households that have age-eligible children will be informed to visit the nearest vaccination centre. If a participant's birth certificate or national immunization cards were not provided during the baseline listing, we will notify their parents or guardians to bring them during vaccination. After arrival at the vaccination centre, the participant and vaccination ID will be verified with the listing database and the master list. Then the screening will be carried out according to inclusion/exclusion criteria.

Informed consent The latest approved version of written informed consent/assent will be presented to the participant's parent/guardian in the local language detailing no less than the exact nature of the study, what it will involve for the participant, the implications and constraints of the protocol, the known side effects and any risks involved in taking part. It will be clearly stated that the participant's parent/guardian is free to withdraw their child from the study at any time for any reason without prejudice to future care, without affecting their legal rights, and with no obligation to give the reason for withdrawal. The participant and their parents/guardians will be allowed as much time as they wish to consider the information, within the recruitment period, and the opportunity to question the investigator or other independent parties to decide whether they will participate in the study. Written informed consent/assent will then be obtained, with additional opt-in consent for blood specimen, using participants' parent/guardian's dated signature or thumbprint and dated signature of the person who presented and obtained the informed consent. Information sheets will be given to children aged 11 -15 years in a language that they can understand. The person obtaining consent will record informed assent on the consent form, for children aged 11 and older. The person who obtained the consent must be suitably qualified and experienced and have been authorized to do so by the Principal Investigator (PI). A copy of the signed informed consent will be given to the participant. The original signed form will be retained at the study site. A third party will act as a witness for the parent/guardian to attest that the information in the consent form and any other written information was accurately explained to, and understood by the parent/guardian and that informed consent was freely given by the parent/guardian. The witness will also sign and date the consent form.

Screening and eligibility assessment An informed written consent will be obtained after confirming the participants by checking the database. After proper consenting process, a temperature will be taken and parents will be asked about antipyretic use and timings of previous vaccination to assess temporary exclusion criteria. A brief medical history will be taken and eligibility will be assessed against inclusion and exclusion criteria. Participants with temporary exclusion criteria will be informed and asked to return 48 hours after the fever has resolved or 30 days after the last vaccination was given for repeat assessment and re-consent. Unmarried girls between the ages of ≥12 to 15 years whose first day of their LMP is more than 28 days or who do not know the date they last menstruated upon presentation will be asked to return after starting their next menstruation, for vaccination. A member of the study team will collect/edit demographic information (including age and address) and participant contact details by screening case report form (CRF). After completion of the eligibility checking, a sticker will be allocated for the participant which includes the information of vaccination ID and temperature; these will be used in the vaccine accountability log.

Vaccination The vaccination team will finally check the identification and then administer the vaccine. After vaccination, information will be recorded in the vaccination CRF. If the participant is included in the immunogenicity study, a blood sample will be taken by a suitably trained staff member before vaccination. After administration of the study vaccine, participants will be asked to wait at least 30 minutes for any immediate hypersensitivity reactions or any other adverse events (AEs). The female participants of reproductive age should have been advised not to be pregnant within three months after the vaccination.

Investigational Medicinal Product (IMP) Purified Vi capsular polysaccharide of Salmonella typhi conjugated to tetanus toxoid as carrier protein (Typhoid Vi Conjugate Vaccine I.P.). Trade name: ZyVac® TCV, Zydus Lifesciences Limited.

Each 0.5ml vaccine dose contains:

Purified Vi-capsular polysaccharide of S.typhi 25 μg Conjugated to tetanus toxoid (carrier protein) 16 to 50 μg 2-Phenoxyethanol (as preservative) 2.50 mg Isotonic buffer solution q.s. The vaccine is packaged as a pre-filled 2.5ml 5-dose vial. It will be administered as an intramuscular injection preferably in the anterolateral aspect of the middle thigh for younger children, or the upper arm for older children with aseptic precautions.

Supply The Vi-TCV vaccine (ZyVac® TCV) will be provided by Zydus Lifesciences Limited.

Storage The Vi-TCV study vaccine will be stored at 2º to 8º C in a temperature monitored icddr,b cold room facilities, when not in use for daily activities. The vaccines will be stored in temperature-monitored refrigerators or cool boxes, when in use for daily activities. Each vial will be labeled with a "vaccine vial monitor"(VVM); a temperature-sensitive dot that provides an indication of the cumulative heat to which the vial has been exposed. It warns the end-user when exposure to heat is likely to have degraded the vaccine beyond an acceptable level and should not be used.

Special precautions for storage Store at 2°C to 8°C. Do not freeze. Discard if frozen. Keep out of reach of children. Shake gently before use. Do not use the vaccine after the expiration date shown on the label

Accountability of the study vaccine The vaccines will be shipped to a central storage facility in Bangladesh and passed through customs. It will then be transported and distributed to local vaccination sites whilst maintaining the cold chain (aiming for a temperature between 2º-8ºC). The number of doses of study vaccines that are received, used, and wasted will be documented daily during the study and checked weekly.

Adverse events following immunization After administration o

• Secondary outcome [Time frame: 12 months]
• Secondary outcome [Time frame: 12 months]