SRP478240 PRJNA1051096 RhCMV/SIV Vaccine Microbiome Study RhCMV/SIV vaccines protect ~50% of vaccinated rhesus macaques against repeated limiting-dose intra-rectal exposure with highly pathogenic SIVmac239m, but the exact mechanism responsible for the 50% efficacy is not known. It is becoming evident that the complex interactions between the gut microbiota and the host immune system can also influence the host response to infection or to vaccination. Here we aim to investigate if the macaque gut microbiome impacts the RhCMV/SIV vaccine-induced protection.