🩹 Shingrix Recombinant Vaccine Efficacy-by-Age Simulator

Pre-Vaccination Zoster Risk

Latent varicella-zoster virus reactivates as immunity naturally declines with age.

• ~33%: Lifetime shingles risk (in unvaccinated adults)
• ~1M: US cases per year (herpes zoster episodes)
• 10–18%: Postherpetic neuralgia (of zoster cases)
• age 50: Risk rises sharply after (immunosenescence onset)

Why zoster risk climbs with age

T-cell immunity to VZV fades gradually after childhood chickenpox.

Waning cell-mediated immunity lets latent virus reactivate in sensory ganglia.

Cell-mediated immunity, not antibody level, is the key barrier against reactivation.

Who is most vulnerable

Adults over 50 and immunocompromised patients face the steepest risk rise.

Complications include postherpetic neuralgia, vision loss, and hospitalization.

The unmet need before recombinant vaccines

Older live-attenuated shingles vaccines lost effectiveness in the oldest patients.

A vaccine strategy independent of age-related immune decline was needed.

Dose 1 — Recombinant gE Antigen Priming

A single recombinant glycoprotein E antigen, paired with adjuvant, primes the immune system.

• gE: Antigen (VZV glycoprotein E)
• AS01B: Adjuvant system (liposome-based)
• Day 0: Dose 1 interval (first injection)
• CD4+ T: Immune cells engaged (and B lymphocytes)

Why gE was chosen as the target

Glycoprotein E is the most abundant VZV surface protein and a dominant immune target.

It anchors both antibody and T-cell recognition of the virus.

The AS01B adjuvant advantage

AS01B combines MPL and QS-21 in a liposome to strongly stimulate innate immunity.

This adjuvant is central to overcoming age-related immune decline.

AS01B, not the antigen alone, is what drives strong response in older adults.

What happens after dose 1

Antigen-presenting cells process gE and activate naive T and B cells.

A measurable but partial immune response builds over the following weeks.

Dose 2 — Immune Memory Consolidation

A second dose 2–6 months later converts a primed response into durable memory.

• 2–6 mo: Dosing interval (between injections)
• 2-dose: Regimen type (series, non-live vaccine)
• Sharp: Memory cell expansion (rise after boost)
• >90%: Efficacy after full series (across trial cohorts)

Why a second dose is essential

A single dose leaves immune memory incomplete and less durable.

The booster recalls and expands memory B and T cells sharply.

Memory B and T cell consolidation

Germinal center reactions mature antibody affinity after the second exposure.

Central memory T cells expand, extending years of protection.

The two-dose series is what makes protection durable, not just initial titer.

Trial evidence behind the interval

ZOE-50 and ZOE-70 trials established the 2–6 month interval as optimal.

Shorter or longer intervals were tested but this window performed best.

Peak Immunity — Antibody and T-Cell Plateau

Antibody titers and T-cell frequency reach their highest post-vaccination levels.

• ~24x: Peak antibody titer (baseline geometric mean)
• ~24x: Peak T-cell frequency (baseline frequency)
• ~1 mo: Time to peak (after dose 2)
• Flat: Response uniformity (across age bands)

Measuring the peak response

Anti-gE antibody concentration and gE-specific CD4+ T cells are both tracked.

Both rise sharply and peak roughly one month after dose 2.

Why older adults still peak strongly

The AS01B adjuvant compensates for the age-related decline in raw immune reserve.

Peak responses in 70+ and 80+ groups closely track younger adults.

Peak magnitude stays comparable across ages — the core efficacy-by-age finding.

From peak response to clinical protection

High peak titer and T-cell counts translate directly into trial-measured efficacy.

This peak is the immunologic basis for the >90% efficacy figure.

Sustained Protection Across All Ages

Efficacy remains flat above 90%, even years later and in the oldest recipients.

• 97.6%: Efficacy, ages 50-70 (ZOE-50 trial)
• 91.3%: Efficacy, ages 70+ (ZOE-70 trial)
• 91.4%: Efficacy, ages 80+ (pooled subgroup analysis)
• >84%: Efficacy at year 4 (long-term follow-up)

The flat efficacy-by-age pattern

Unlike most vaccines, efficacy does not decline meaningfully with age.

This distinguishes Shingrix from earlier live-attenuated shingles vaccines.

The oldest age group protects nearly as well as the youngest — a rare vaccine trait.

Why durability holds in older adults

Strong adjuvant-driven priming leaves a durable memory pool despite immunosenescence.

Memory cells decline slowly rather than immunity never fully forming.

Public health implications

Recommended for adults 50+ regardless of prior shingles or chickenpox history.

Broad, age-independent efficacy simplifies vaccination guidance globally.