Non-interference Study of MR and Yellow Fever Vaccines Among Bangladeshi Infants Aged 9-12 Months

This study will be conducted among 1530 healthy infants of 9 to 12 months of age residing in the Dakshinkhan and Uttarkhan area which is located in Dhaka North City Corporation (DNCC) to enroll the required number of participants. Only infants who have not previously received the MR and YF vaccines will be enrolled. The findings of this study are likely to have a significant impact on vaccine co-administration strategies for campaign and routine immunization programs. The participants will be assigned to one of the three groups by the central computer-generated randomization schedule. The numbers are defined for each arm (Table 1) based on the sample size calculation. A list of infants who did not receive MR and Yellow fever vaccine will be prepared before enrollment by trained study staff (TSS). The TSSs will visit households in the defined study area and ask if the parents/guardians of infants aged 9-12 months are willing to participate in the study. If they show a willingness to participate, the TSSs will check their vaccination cards (if available) and prepare the list of potentially eligible infants who have not received MR and Yellow fever vaccines based on their vaccination card status. The investigators will collect blood specimens (4-5 ml) at the time of screening (visit-1), to evaluate serological markers of dengue and Japanese Encephalitis infection and for baseline (pre-vaccination) immunological assessment. The investigators will vaccinate seronegative, eligible participants within 24 hours of blood collection. There will be additional three follow-up visits after enrollment and will collect around 3-4 ml blood from each participant during visit 4 (week 6), and visit 5 (week 26) for immunological assessment. Diary cards will be used to collect adverse events (AEs) following immunization (AEFI) data for vaccinated participants (up to 14 days for solicited and 6 weeks for unsolicited AEs). Medically attended adverse events (MAAEs) and data on serious adverse events (SAEs) will be reported during the study. All study updates including AEs and SAEs will be reported to the data safety and monitoring board (DSMB) and sponsor.