Decline of Subacute Sclerosing Panencephalitis Mortality Linked With Increased Vaccinations

Age-specific mortality from subacute sclerosing panencephalitis (SSPE), the neurodegenerative disease caused by the measles virus, is reflective of changes in measles age distributions, and the condition could disappear in the United States if measles vaccination rates remain high, according to data published in Vaccine.

Publicly available information on deaths in the United States from 1979 to 2016 was used to extract data on recorded SSPE mortality. Specifically, death certificates indicating SSPE as the cause of death were compiled. No clinical information was collected.

Investigators found that SSPE is an extremely rare cause of death and that rates have declined over time since 1979. Younger individuals, between infancy and 9 years of age, are largely unaffected because of the long incubation period of the virus. Individuals aged 10 to 24 years saw the most recorded cases of SSPE mortality. SSPE mortality also followed a shift in the age distribution of measles during the 1970s, with individuals aged 25 to 64 years seeing an increase in SSPE mortality. This should be interpreted in the context of measles incubation periods and several severe outbreaks in the 1970s. A noticeable and anomalous number of 10 deaths in the youngest age group in 1995 to 1998 was also likely a result of a measles epidemic that occurred in 1989 to 1991.

Information on when individual patients contracted measles was unavailable; however, investigators conclude, “the patterns reflect those of measles epidemiology, taking into account changes in age profiles of cases, and the long incubation period of SSPE.” Investigators also believe that with continued vaccination the disease will vanish entirely in the United States. In Europe, however, where a large measles outbreak is underway, SSPE should continue to be monitored.

Reference

Pallivathucal LB, Noymer A. Subacute sclerosing panencephalitis mortality, United States, 1979-2016: Vaccine-induced declines in SSPE deaths. Vaccine. 2018;36:5222-5225.