Mumps Outbreak in Shivamogga, India (2023-2024): Age-Specific Attack Rates, Complications, and an Economic Case for Measles-Mumps-Rubella Vaccine Inclusion in the Universal Immunization Programme.

Background Recurrent mumps outbreaks continue to be reported in India, where the vaccine is not part of the national immunization schedule. Robust, age‑specific burden data from outbreak settings remain limited. Methods We conducted a retrospective investigation of pediatric mumps during epidemiologic weeks (EW)49‑2023 to EW8‑2024 across Subbaiah Institute facilities in Shivamogga, Karnataka, India. Clinically suspected cases were line-listed; laboratory confirmation used anti-mumps IgM enzyme-linked immunosorbent assay (ELISA). We described demographics, complications, and length of stay (LOS) among IgM‑confirmed cases, estimated age‑specific attack rates using district population denominators, and compared complication risks by age with exact tests and risk ratios (RRs; 95% CI). Vaccination status was ascertained from immunization cards/registers where available, otherwise by parental recall. Results Among approximately 2,500 clinically suspected cases during EW49-2023 to EW8-2024, 318 children (median age 6.5 years (IQR five to nine years); 49% female) were IgM-confirmed. The overall attack rate among children aged one to 16 years was 69 per 100,000 (95% CI 61.6-77.0), highest in the five-to-nine-year-old group (147 per 100,000) compared with <5 years (70 per 100,000) and ≥10 years (13 per 100,000). Nine children (2.8%, 95% CI 1.3-5.2) developed complications such as pancreatitis (0.9%), aseptic meningitis (0.9%), orchitis (0.6%), and oophoritis (0.3%). Complication risk increased with age: 0% in <5 years, 1.9% in five to nine years, and 19.2% in ≥10 years (RR 10.1, 95% CI 3.0-34.3; Fisher's p < 0.001). All confirmed cases were unvaccinated for mumps. Median hospital stay was six days (IQR three to seven days) for complicated vs. three days (IQR two to four days) for uncomplicated cases. Conclusion This outbreak disproportionately affected school‑aged children, with complications concentrated in those ≥10 years. Findings quantify the preventable disease burden and support inclusion of a two-dose measles-mumps-rubella (MMR) vaccination schedule in India's Universal Immunization Programme (UIP), along with a catch-up vaccination strategy for children and adolescents aged between five and 15 years. Observed hospitalization burden highlights potential economic relevance; however, no formal cost-effectiveness or budget-impact analysis was performed.