Yellow Fever

RACSMEI addresses the high burden of infectious diseases in low- and middle-income countries, including Cambodia, where limited surveillance and laboratory capacity often obscure etiologies and transmission dynamics. This knowledge gap hinders the design of effective prevention and control strategies. RACSMEI will improve understanding across multiple pathogens using a multidisciplinary One Health approach. We will answer key questions on burden, ecology, transmission and population immune status to inform targeted and culturally appropriate interventions. The project combines a nationally representative One Health survey, social-science methods, and multiplex, diverse diagnostics to efficiently test for 57 priority pathogens, including zoonotic and vector-borne agents, vaccine-preventable and elimination-targeted diseases, enteric, respiratory, and environmentally transmitted pathogens and selected neglected tropical diseases and parasites relevant to Cambodia. Mathematical modelling will reconstruct and forecast transmission dynamics and assess the potential impact of future public-health strategies. By integrating intersectoral data and innovative methods, RACSMEI will generate actionable evidence for public-health authorities, support precision One Health interventions, and help reduce disease burden in affected communities. The project also aims to ensure the transferability of methods and insights to other countries facing similar challenges.

The goal of this clinical trial is to assess the immune response to the yellow fever vaccine 17D in adults with prior 17D vaccination. The main questions this study aims to answer are: * how does prior vaccination affect antibody responses to re-vaccination? * how does prior vaccination affect the immune cell response to re-vaccination? Participants will: * have been previously vaccinated with 17D. * be re-vaccinated with 17D. * provide medical and travel histories. * provide a blood sample prior to vaccination * provide a blood sample approximately every other day for 14 days after vaccination. * provide a blood sample approximately 28 days after vaccination. * complete a daily diary of symptoms following vaccination for 14 days. * report any additional symptoms after 14 days.

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.

ANRS 0146s NovaaTen study aims to determine the vaccine responses in the participants of the ANRS EP46 Novaa trial 10 years after a primary anti-yellow fever vaccination