SSPE Risk After Age 5: Not Negligible
The statement that measles after age 5 carries negligible risk for SSPE is FALSE—while the risk is substantially lower than in younger children, it remains clinically significant and measles vaccination remains the only effective prevention strategy regardless of age. 1, 2
Age-Stratified Risk Profile
The risk of SSPE following measles infection is strongly age-dependent but never truly negligible:
- Measles infection under 1 year of age carries a risk 16 times greater than measles contracted after age 5 years 3
- The highest risk occurs in children who contract measles before age 5 years, particularly under age 2 years 4, 5
- However, measles contracted after age 5 still carries a baseline risk of approximately 4-11 per 100,000 measles cases 6, 3
This "lower" risk after age 5 must be contextualized: the actual risk is substantially underestimated because only about 11% of measles infections are officially reported, meaning the true denominator of measles cases is much larger than surveillance data suggest 6. When accounting for underreporting, even the "reduced" risk in older children represents meaningful clinical danger.
Clinical Implications for Vaccination
The Advisory Committee on Immunization Practices (ACIP) definitively states that all children should receive two doses of MMR vaccine regardless of age, as measles vaccination has essentially eliminated SSPE in highly vaccinated populations 1, 2:
- First dose at 12-15 months of age 2
- Second dose at 4-6 years to address the approximately 5% primary vaccine failure rate 2
- Catch-up vaccination for adolescents and adults born after 1957 without documentation of two MMR doses 2
Critical Evidence on Disease Progression
SSPE typically presents 6-8 years after the initial measles infection, with onset generally between ages 5-15 years 1, 3. This means:
- A child infected with measles at age 6 could develop SSPE in adolescence
- The median 8-year interval between measles and SSPE onset means cases continue to emerge years after the initial infection 3
- Age at onset of SSPE has increased significantly over time as vaccination programs have reduced early childhood measles 3
Prognosis Considerations
Survival time following SSPE diagnosis was actually shorter when the initial measles infection occurred over the mean age of 2.5 years 3. This counterintuitive finding suggests that while younger age at measles infection increases SSPE risk, older age at infection may be associated with more aggressive disease progression once SSPE develops.
Common Pitfalls to Avoid
- Do not confuse lower relative risk with negligible absolute risk—even the reduced risk after age 5 represents preventable mortality and severe morbidity 4, 5
- Do not assume MMR vaccine increases SSPE risk—the ACIP definitively states that MMR vaccination does not increase SSPE risk, even in persons who previously had measles 1, 2
- Do not delay vaccination based on age considerations—vaccination remains the only effective prevention strategy at all ages 1, 2, 7