Number Needed to Treat (NNT) for Shingrix Vaccine
The NNT for Shingrix to prevent one case of herpes zoster is 33 over 3.2 years of follow-up, based on the most recent high-quality trial data.
Primary Efficacy Data
- Shingrix demonstrates an NNT of 33 to prevent one case of herpes zoster at 3.2 years of follow-up in adults aged 50 years and older 1
- The vaccine achieves 97.2% efficacy in preventing herpes zoster in adults aged ≥50 years in the ZOE-50 trial 1
- This translates to an absolute risk reduction of 3% (risk difference) for preventing herpes zoster 1
Comparison to Previous Vaccine (Zostavax)
For context, the older live-attenuated Zostavax vaccine had substantially different efficacy:
- Zostavax showed 51.3% efficacy in preventing herpes zoster in adults aged ≥60 years 2
- The NNT for Zostavax was approximately 50 to prevent one case of herpes zoster over 3 years 1
- Zostavax efficacy declined markedly with age: 70% in ages 50-59 versus only 18% in those ≥80 years 3
Real-World Effectiveness
- Post-licensure real-world data shows 70.1% effectiveness for the complete 2-dose Shingrix series in Medicare beneficiaries aged >65 years 4
- Single-dose effectiveness was lower at 56.9%, emphasizing the importance of completing both doses 4
- Real-world effectiveness estimates are lower than clinical trial efficacy due to differences in outcome specificity and population characteristics 4
Prevention of Postherpetic Neuralgia (PHN)
- Shingrix demonstrates 76.0% effectiveness against postherpetic neuralgia in real-world settings 4
- This represents a critical benefit given that PHN is the most debilitating complication of herpes zoster 2
Duration of Protection
- Protection persists for at least 8 years with minimal waning, maintaining efficacy above 83.3% during this period 1
- This sustained protection is superior to Zostavax, which showed significant waning from 51.3% to 21.2% efficacy during years 7-11 post-vaccination 3
Clinical Implications
- The NNT of 33 represents excellent vaccine performance, particularly for a condition with significant morbidity in older adults 1
- Shingrix maintains high efficacy across all age groups, unlike Zostavax which had markedly reduced effectiveness in the oldest populations 1, 3
- The vaccine is administered as a 2-dose series with doses given 2-6 months apart for optimal protection 1