Changing Trends of Subacute Sclerosing Panencephalitis— Pre- and Postvaccination Era, Why Should Children Vaccinated against Measles Develop SSPE?

Introduction: Subacute sclerosing panencephalitis (SSPE) is thought to occur several years after measles infection. Measles vaccine is protective against SSPE. However, SSPE has been reported in vaccinated children without prior history of measles infection.

Materials and Methods: A retrospective study was done to analyze vaccinated children with SSPE without prior history of measles infection.

Results: Fifteen out of 22 cases of SSPE in the past 10 years were immunized for measles. Mean age of onset was 8.4 years with 80% of children being under 10 years of age. Average time of progression to advanced stage of the disease was 2.5 months–3 months (range:15 days–5 months).

Discussion In vaccinated children, a subclinical or unrecognized measles infection is speculated to be the source of wild virus, with exposure occurring before vaccination. Earlier the age of exposure, higher is the risk of SSPE. Although thought to be slowly progressive, recent trend indicates a younger age of onset and faster progression of SSPE from onset to critically disabling stages. Vaccination with measles at 9 months changes the epidemiology of SSPE leaving younger infants susceptible to measles. Also, as per previous studies, maternally acquired antibodies probably wane off by 3 to 4 months. With current immunization schedule of administering first dose of measles vaccine at 9 months, children less than 9 months remain susceptible to measles and later SSPE. However, vaccination before 9 months is found to be both effective and safe.

Conclusion: This study proposes a relook at the need of reducing the age of vaccination against measles to 6 months.