The Statement is FALSE: Age 5 Does NOT Confer Negligible SSPE Risk
The claim that SSPE risk becomes negligible at age 5 is incorrect—while children who contract measles before age 5 (especially under 12 months) have the highest risk, measles infection at any age can lead to SSPE, and the only effective prevention is measles vaccination regardless of age. 1
Why This Misconception is Dangerous
The statement conflates two separate concepts:
- Age at measles infection (the actual risk factor)
- Age at SSPE diagnosis (which typically occurs 6-8 years after measles infection) 1
Children infected with measles under age 5 have the highest SSPE risk (approximately 1 in 609 for those infected before 12 months, and 1 in 1,367 for those infected before age 5), but measles infection at older ages still carries substantial risk. 2, 3
The Critical Evidence
Age-Specific Risk Data
- Among California measles cases from 1988-1991, SSPE incidence was 1:609 for children infected before 12 months and 1:1,367 for children infected before 5 years 3
- The overall SSPE rate is approximately 4-11 per 100,000 measles infections across all ages 1, 2
- SSPE typically presents 6-8 years after initial measles infection, with onset generally between ages 5-15 years 1
The Immune System Argument is Flawed
The statement's premise about immune maturity at age 5 preventing viral persistence is not supported by evidence:
- SSPE results from persistent mutant measles virus in the CNS, not from inadequate initial immune clearance 4
- The disease develops through viral persistence mechanisms years after the acute infection, when systemic immunity has long been established 4
- Even immunologically normal individuals develop SSPE through mechanisms that remain incompletely understood 5, 4
Clinical Implications
Vaccination Remains Essential at All Ages
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
- First dose: 12-15 months (or at 12 months in high-risk areas) 1
- Second dose: 4-6 years 1
- The second dose addresses the approximately 5% primary vaccine failure rate from the first dose 1
Adolescents and adults born after 1957 without documentation of two MMR doses should receive catch-up vaccination 1
Common Pitfalls to Avoid
- Do not assume that a 5-year-old who contracts measles is protected from SSPE by immune maturity 1
- Do not confuse the age at measles infection with the age at SSPE diagnosis—these are separated by years 1, 3
- Do not delay vaccination based on age-related risk stratification—vaccination is the only effective prevention at any age 1, 6, 7
The Devastating Reality of SSPE
- SSPE is uniformly fatal in most affected children 1, 2
- Younger children (under age 4 at SSPE diagnosis) appear to have particularly poor prognosis with rapidly progressive courses 8
- There is no cure—treatments are supportive only 2, 7
The only protection strategy is prevention of measles infection through vaccination, which has essentially eliminated SSPE in highly vaccinated populations. 1, 6, 7