MMR vaccine dosage does not provide herd immunity in mumps outbreak, Finds study

Mumps is a vaccine-preventable viral respiratory illness mainly in the pediatric age group. Epididymo-orchitis is the most common complication and meningoencephalitis is the most common cause of mortality in mumps. Sporadic outbreaks of mumps are reported from India and other countries indicating a resurgence of the disease in both vaccinated and unvaccinated populations. Outbreaks in vaccinated young adults indicate waning of immunity with time.

Considering the paucity of data regarding sero-protectiveness in children against mumps, Bhoomika Saxena and colleagues from the Department of Microbiology and Pediatrics, University College of Medical Sciences and Guru Tegbahadur hospital, Delhi, India carried out the study to compare the level of mumps specific antibodies in MMR vaccinated and vaccine naive healthy children.

The authors conducted this cross-sectional study was conducted at a tertiary-care public hospital in Delhi among 78 healthy children aged 16 month-12 years attending the pediatric outpatient department. Serum igg and IgM rubella antibodies were measured by Elisa for confirmation of MMR vaccination status. Qualitative determination of IgG mumps was done followed by the quantitative determination in samples positive for igg mumps antibodies.

The study revealed that the IgG mumps was present in 69.2% of the study population, with seroprotective titers in 32% taking endpoint titer as 1:4. Among MMR vaccinated children, 41.1% were sero-protected and in MMR vaccine naïve children 9.1% were seroprotected for mumps.

Low rate of seroprotection among MMR vaccinated children can be attributed to failure of development of immunity with a single dose of vaccine or failure of vaccine uptake. Rate of subclinical infection and atypical presentation in mumps are known to be very high.

Hence, a single dose of MMR vaccine does not provide effective (>90%) seroconversion required for successful herd immunity to prevent mumps outbreak, the authors concluded.