Absolute Risk Reduction of Shingrix for Preventing Shingles
Shingrix provides an absolute risk reduction of approximately 8.4 per 1,000 person-years in adults aged 70 years and older, translating to preventing roughly 8-9 cases of shingles per 1,000 people vaccinated annually.
Efficacy Data from Pivotal Trials
The absolute risk reduction varies by age group based on the baseline incidence rates in different populations:
Adults Aged 70 Years and Older
- In the ZOE-70 trial, the incidence rate of herpes zoster was 0.9 per 1,000 person-years in the Shingrix group compared to 9.2 per 1,000 person-years in the placebo group 1
- This yields an absolute risk reduction of 8.3 per 1,000 person-years 1
- The relative risk reduction (vaccine efficacy) was 89.8% in this age group 1
Adults Aged 50 Years and Older
- In the ZOE-50 trial, Shingrix demonstrated a vaccine efficacy of 97.2% across all age groups 50 years and older 2
- The absolute risk reduction in this broader population reflects the lower baseline incidence in younger adults compared to those 70+ years 2
Pooled Analysis (Ages 70+)
- Combining data from both ZOE-50 and ZOE-70 trials for adults aged 70 years and older showed an incidence rate of 0.8 per 1,000 person-years with Shingrix versus 9.3 per 1,000 person-years with placebo 1
- This represents an absolute risk reduction of 8.5 per 1,000 person-years 1
- The vaccine efficacy was 91.3% in this pooled analysis 1
Age-Stratified Absolute Risk Reduction
The absolute benefit increases with age due to higher baseline shingles incidence:
- Ages 70-79 years: Incidence was 0.8 per 1,000 person-years (Shingrix) vs 8.9 per 1,000 person-years (placebo), yielding an absolute risk reduction of 8.1 per 1,000 person-years 1
- Ages 80+ years: Incidence was 1.0 per 1,000 person-years (Shingrix) vs 11.1 per 1,000 person-years (placebo), yielding an absolute risk reduction of 10.1 per 1,000 person-years 1
Postherpetic Neuralgia Prevention
Shingrix also provides substantial absolute risk reduction for postherpetic neuralgia (PHN):
- In adults aged 70+ years, the incidence of PHN was 0.1 per 1,000 person-years with Shingrix versus 1.2 per 1,000 person-years with placebo 1
- This represents an absolute risk reduction of 1.1 per 1,000 person-years for PHN 1
- The vaccine efficacy against PHN was 88.8% in this population 1
Real-World Effectiveness Data
Post-licensure studies show slightly lower but still substantial effectiveness:
- A large Medicare cohort study found real-world vaccine effectiveness of 70.1% for the complete 2-dose series, which is lower than the clinical trial efficacy of >90% 3
- The difference between trial efficacy and real-world effectiveness likely reflects less stringent outcome definitions in routine practice compared to PCR-confirmed cases in trials 3
- Real-world effectiveness against PHN was 76.0% 3
Clinical Context and Number Needed to Vaccinate
To prevent one case of shingles annually:
- In adults aged 70-79 years: approximately 120 people need to be vaccinated (based on absolute risk reduction of 8.1 per 1,000 person-years) 1
- In adults aged 80+ years: approximately 100 people need to be vaccinated (based on absolute risk reduction of 10.1 per 1,000 person-years) 1
To prevent one case of PHN annually:
- In adults aged 70+ years: approximately 910 people need to be vaccinated (based on absolute risk reduction of 1.1 per 1,000 person-years) 1
Durability of Protection
- Protection remains robust with efficacy maintained above 83.3% for at least 8 years post-vaccination 2, 4
- At 10 years, efficacy decreases to approximately 73% 2
- In the fourth year after vaccination, efficacy against herpes zoster was 85.1% in adults aged 70+ years 1
Comparison to Previous Vaccine
Shingrix provides substantially greater absolute benefit than the older Zostavax vaccine: