SSPE Incidence Following Measles at Age 5
The incidence of SSPE following measles infection at age 5 is approximately 4-11 per 100,000 measles cases, which represents a substantially lower risk compared to measles contracted before age 5, particularly in infancy.
Age-Stratified Risk Profile
The risk of SSPE varies dramatically by age at measles infection:
- Infants under 12 months: The highest risk group, with an incidence of approximately 1 in 609 measles cases (164 per 100,000) 1
- Children under 5 years: Overall incidence of 1 in 1,367 measles cases (73 per 100,000) 1
- Children over 5 years: Measles contracted after age 5 carries a risk approximately 16 times lower than measles under 1 year of age 2
Critical Context for Age 5 Specifically
For a child contracting measles at exactly age 5, the SSPE risk falls at the lower end of the spectrum, likely in the range of 4-11 per 100,000 cases 3, 4. This represents the general population risk rather than the elevated risk seen in younger children 5.
Important Caveats About Risk Calculation
- These figures are based on reported measles cases, which historically represented only about 11% of actual infections, meaning the true per-infection risk may be lower than these estimates suggest 4
- The latency period between measles infection and SSPE onset averages 8-9.5 years, with a range of 2.5-34 years 1, 2
- Males have a 2.4-2.8:1 higher risk compared to females 1, 2
Additional Risk Factors Beyond Age
Even at age 5, certain conditions increase SSPE risk:
- Immunocompromised states: Children with HIV infection, leukemias, or lymphomas face increased risk of both severe measles and subsequent SSPE 6, 3
- Geographic factors: Children in areas with poor vaccination coverage and high HIV prevalence have elevated risk 5
Prevention Imperative
Measles vaccination remains the only effective prevention strategy and has essentially eliminated SSPE in highly vaccinated populations 6, 3, 4. The MMR vaccine does not increase SSPE risk, even in persons who previously had measles 4.
Clinical Recognition
Clinicians should maintain awareness of SSPE in patients presenting with progressive neurological deterioration, even in older patients without documented measles history, given the long latency period and the fact that 25-50% of measles cases may be subclinical 7, 1.