SSPE Risk at Age 5
The risk of SSPE after measles infection at age 5 is approximately 1 in 1,700 to 1 in 3,300 (or roughly 4 per 100,000 measles cases). 1
Age-Specific Risk Stratification
The risk of SSPE varies dramatically by age at measles infection:
- Under 1 year of age: Highest risk at approximately 1 in 609 (or 18 per 100,000 measles cases) 2, 3
- Under 5 years of age: Elevated risk at 1 in 1,700 to 1 in 3,300 1
- Over 5 years of age: Risk is 16 times lower than measles contracted under 1 year 4
Children who contract measles at age 5 fall into the "under 5 years" category, which carries substantially elevated risk compared to older children, though lower than infants. 5, 1
Overall Population Risk
The general population risk across all ages is approximately 4-11 per 100,000 measles infections 6, 5, with the CDC and WHO noting that the overall calculated risk is 4.0 per 100,000 cases 2, 4.
Critical Context
The statement that measles after age 5 carries negligible risk for SSPE is definitively false. 6 While the risk decreases with increasing age at infection, children infected at age 5 remain in the high-risk category, with SSPE risk in the same order of magnitude as the risk of fatal acute measles infection itself 1.
Among documented SSPE cases, 71% had measles-like illness prior to 15 months of age, and nearly half of all cases with documented measles had the infection under 2 years 3, 4. However, this does not mean older children are protected—it reflects the epidemiologic pattern of when measles typically occurs in unvaccinated populations.
Latency Period
SSPE typically presents 6-8 years after the initial measles infection, with onset generally between ages 5-15 years, though the latency period can range from 2.5 to 34 years 6, 3.