Continuing mumps outbreak in Keralam leads to renewed demand for MMR vaccine

The continuing mumps outbreak in Keralam, which began in late 2023 and has persisted into 2026, has renewed demands for including the mumps-measles-rubella (MMR) vaccine in the Universal Immunisation Programme (UIP). Outbreaks have forced the closure of schools and hostels for weeks in Alappuzha, Thrissur and Kottayam.The demand has gained strength following studies from Keralam documenting immunity gaps among children, complications that can cause long-term disability, and genetic differences between the circulating mumps virus and the strain used in the vaccine, indicating how the continued exclusion of the MMR vaccine from the UIP represented an important gap in disease prevention.From an annual average of over 2,000 cases, mumps infections began surging in November 2023. Keralam reported 74,907 cases in 2024 and 26,462 in 2025. A further 6,606 cases have been reported so far this year.Low priorityDespite being vaccine-preventable, mumps has remained a relatively low priority in India’s immunisation policy, largely because of its low mortality. Although a time-tested combined MMR vaccine is available, the UIP provides two doses of the measles-rubella (MR) vaccine, which does not protect against mumps.The Indian Academy of Paediatrics (IAP) has long recommended MMR in place of MR, a vaccine combination available to children through the private sector since the 1980s. It has argued that mumps’ public health significance is underestimated because clinical cases, complications and long-term outcomes are inadequately documented.With outbreaks also occurring regularly in other States, several have urged the Centre to include MMR in the UIP.In a response to the Tamil Nadu government obtained through an RTI application, the Centre said decisions on introducing vaccines under the UIP consider disease prevalence and incidence, mortality, vaccine efficacy and cost-effectiveness, among other factors.According to the response, the National Technical Advisory Group on Immunisation (NTAGI) considers mumps-associated disability not a significant public health concern. Adding the mumps component, it said, would more than double the vaccine’s cost compared with MR, without proportionate additional health benefits.‘Poorly documented’Paediatricians contest this assessment, arguing that the disease burden and long-term complications of mumps remain poorly documented.“The increased cost argument is being made in a setting where the mumps burden and associated long-term complications are poorly documented. Systematic surveillance, documentation of complications and disabilities, transparent vaccine-price comparisons and an economic evaluation factoring in health-care costs, school absenteeism and complications should settle this,” they say.“Mumps may not cause mortality, but its morbidity is significant, particularly during epidemics among unimmunised children. Complications include acute pancreatitis, encephalitis and aseptic meningitis. The virus can affect the reproductive glands in both sexes, with long-term consequences that may not be immediately apparent. It is also a leading cause of acquired sensorineural hearing loss in children, sometimes resulting in permanent, irreversible deafness due to nerve damage,” says K.K. Purushothaman, former Professor of Paediatrics, Government Medical College, Thrissur.He also questions whether the Centre has applied consistent standards of evidence and affordability when deciding which vaccines merit public funding, given the subsequent inclusion of relatively expensive vaccines such as the pneumococcal conjugate vaccine (PCV) in the UIP and later the HPV vaccine (as a special initiative). MMR, he argues, is a time-tested and safe option that has not been assessed against current evidence using comparable cost-effectiveness standards.Molecular characterisationA study by the Keralam unit of the National Institute of Virology, published in Infection, Genetics and Evolution in September 2026, adds another dimension to the debate. Molecular characterisation of mumps viruses circulating in Keralam during 2024–25 identified genotype C, genetically different from genotype N (L-Zagreb), the strain used in the mumps vaccine.The researchers emphasised the need for continued molecular surveillance to track viral evolution and evaluate the current vaccination strategy. However, genetic differences alone do not establish that the vaccine is ineffective.The study noted that available seroepidemiological evidence and outbreak patterns indicate a considerable mumps burden. The continued exclusion of a mumps vaccine from the UIP, it suggested, leaves an important gap in disease prevention.