🩹 Postherpetic Neuralgia Risk Reduction Simulator

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.