Efficacy inputs are among the key drivers of the cost-effectiveness of any intervention. The authors derive 1-dose efficacy inputs of 78% for V-MSD from a methodological study using a statistical model  relating immunogenicity data (varicella-zoster virus antibody titer, >5 glycoprotein enzyme-linked immunosorbent assay units per milliliter, 6 weeks after vaccination) to long-term disease breakthrough. The efficacy estimate reported  was based on antibody titer with predicted efficacy of 94.0% for all ages and 87.2% in younger children (n = 326; median age, 13 months). However, Akpo et al  used predicted efficacy of 78% from sensitivity analysis that was included to illustrate the impact of a 2-fold decrease in antibody titer on efficacy (from 88% to 78%) in children who were vaccinated at age 18 months.
While immunogenicity data can be used as a correlate of protection, using predicted efficacy based on antibody titers alone is a limitation given actual efficacy data is available for V-MSD. Several randomized control trials (RCTs) and observational studies have been published, demonstrating the long-term efficacy [3–6] and effectiveness of V-MSD [7–9]. Kuter et al , in an RCT with 10 years of follow-up, showed that 1-dose efficacy of V-MSD was 94.4% (95% confidence interval, 92.9%–95.7%), and 2-dose efficacy was 98.3% (97.3%–99.0%).
Reference link- https://academic.oup.com/cid/article/73/5/935/6122568