Abstract
Typhoid fever, measles, and rubella continue to contribute significantly to childhood morbidity and mortality in India. In line with WHO recommendations for co-administration of Typhoid Conjugate Vaccine (TCV) and measles-rubella (MR) vaccine at 9 months of age, this phase IV, randomized, open-label, multicenter clinical trial was conducted to assess their immunological compatibility and safety when administered concomitantly. A total of 900 healthy Indian infants aged 9-10 months were randomized into three groups: Group A received TCV and MR vaccine concomitantly; Group B received MR on Day 0 and TCV on Day 28; Group C received TCV on Day 0 and MR on Day 28. Subjects were followed for 6 months after concomitant/last vaccination. Seroconversion rates (SC) in Groups A/B/C at Day 28 were 90.2%/75.3%/89.5% for anti-Vi; 80.4%/75.2%/77.7% for anti-measles, and 87.7%/84.0%/85.2% for anti-rubella antibodies. By study end, SC for anti-Vi was 87.1%/71.6%/83.0%, while SC for anti-measles and anti-rubella reached ~90% and ≥98%, respectively, across all groups. Geometric mean titers increased significantly for all antigens, with no evidence of immunological interference. Safety assessments showed adverse events in 23.9%/32.0%/32.7% participants in Group A/B/C. Most adverse events were mild, and only one serious adverse event was reported. These findings support the co-administration of TCV and MR vaccine as a safe and effective strategy.