Unvaccinated Shingles Episode
Dormant varicella-zoster virus reactivates, inflaming sensory nerve fibers.
- 1 in 3: Lifetime shingles risk (general population)
- ~1 M: Annual U.S. cases (new cases yearly)
- 10–18%: PHN incidence (of unvaccinated cases)
- 90%+: Shingrix efficacy (against shingles)
Viral reactivation
Weakened immunity lets latent virus reawaken in ganglia.
Reactivation risk rises sharply after age fifty.
Sensory ganglion inflammation
Inflammation spreads along dorsal root ganglion neurons.
Early nerve involvement
Nerve fibers sustain injury even before rash appears.
Nerve Fiber Damage
Inflamed nerve fibers develop aberrant, pain-generating signaling patterns.
- Variable: Affected sensory axons (depends on outbreak severity)
- Significant: Myelin loss (around inflamed segments)
- Days: Aberrant signal onset (after inflammation begins)
- Possible: Central sensitization (spinal cord involvement)
Axonal injury
Viral inflammation strips myelin from sensory axons.
Damaged axons fire pain signals without any stimulus.
Aberrant signaling
Injured fibers generate spontaneous, abnormal pain impulses.
Central sensitization
Spinal neurons grow hyperexcitable from sustained input.
Acute Rash Resolves
Skin lesions heal while underlying nerve damage may persist.
- 2–4 wks: Rash duration (typical healing time)
- Healed: Skin appearance (lesions crust and fade)
- Incomplete: Nerve recovery (for many patients)
- 90+ days: PHN definition (pain after rash onset)
Rash resolution
Vesicles crust over and skin looks normal again.
Healed skin can mask lingering nerve damage.
Silent nerve scarring
Damaged fibers stay scarred beneath healed skin.
Risk window opens
Pain persisting past healing signals possible PHN.
Postherpetic Neuralgia Develops
Chronic pain persists long after the rash has healed.
- Up to 30%: PHN risk, age 70+ (age-dependent risk)
- Months–years: Pain duration (for some patients)
- Reduced: Quality of life (by chronic pain)
- Partial: Treatment success (therapies rarely cure it)
Chronic pain state
Aberrant signaling becomes a persistent pain disorder.
Older, unvaccinated patients face the highest PHN risk.
Age-dependent severity
Risk and duration both climb steeply with age.
Limited treatment options
Current therapies manage, rarely eliminate, chronic pain.
Vaccinated Comparison
Vaccination sharply lowers shingles severity and PHN risk.
- ~90%: Shingrix efficacy vs PHN (risk reduction)
- 2 doses: Dose schedule (recommended for adults 50+)
- Milder: Breakthrough cases (when vaccinated)
- Years: Protection durability (sustained risk reduction)
Vaccine protection
Shingrix trains immunity to blunt viral reactivation.
Vaccination cuts PHN risk by roughly ninety percent.
Milder breakthrough disease
Vaccinated breakthrough cases cause far less nerve damage.
Population impact
Widespread vaccination could prevent most PHN cases.