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P7 Evaluating Impact of Universal Varicella Vaccination Strategies on Clinical Burden of Varicella and Herpes Zosterin England and Wales

      Objectives

      England and Wales have not implemented universal varicella vaccination (UVV) primarily due to its hypothesized impact on herpes zoster (HZ) incidence. Our study evaluated long-term clinical impact of UVV and exogenous boosting on varicella and HZ in England and Wales.

      Methods

      An age-structured, deterministic, dynamic transmission model using a dynamic population was adapted to England and Wales to assess varicella cases, associated hospitalizations and HZ cases. Ten (one- and two-doses, with/ without catch-up) vaccination strategies at short (12m/18m) and medium (18m/40m) dose intervals with and without catchup for 2 doses at 14 and 15 years of age were compared to no vaccination over a 50-year time horizon. Four varicella vaccines were considered with monovalent and quadrivalent formulations [Varivax®, ProQuad® (V/MMRV-MSD) Varilrix® and Priorix-Tetra®(V/MMRV-GSK)]. Vaccination coverage was assumed to be 91% for first doses and 89% for 2nd doses and 87% for catch-up. The model accounted for the impact of exogenous boosting on HZ cases.

      Results

      All vaccine strategies substantially reduced the clinical burden of varicella over no vaccination: with 82-97% reduction in total varicella cases and 78%-86% reduction in the number of hospitalizations. One-dose strategies without catchup resulted in the smallest reduction in cases, hospitalizations, while the greatest reduction was seen with the 2-dose short-interval (12m and 18m) strategy. Incidence of HZ is estimated to be reduced by 7-11%. Strategies with V/MMRV-MSD vaccines were more effective in averting all four outcomes than with V/MMRV-GSK vaccines with similar intervals.

      Conclusions

      Our model estimated that all one and two-dose UVV strategies significantly reducted the clinical burden of varicella including reduction in varicella related incidence, and hospitalization as well as reduction in HZ incidence compared to no vaccination in England and Wales. Policymakers should consider including UVV in their childhood immunization program to reduce disease burden.