Modelling Hospitalisation Ratios for Febrile Convulsions and Severe Varicella Under Combined Measles, Mumps, Rubella, and Varicella (MMRV—Priorix-Tetra™) Compared to Separate MMR + V Vaccination

INTRODUCTION: Measles, mumps, rubella, and varicella combination vaccines (MMRV) facilitate varicella vaccination uptake compared with separate administration of measles, mumps, and rubella vaccine (MMR) with varicella vaccine (V). However, the risk of developing febrile convulsions (FC) is higher in children vaccinated with MMRV. OBJECTIVES: The aim was to demonstrate how to put the increased FC risk associated with MMRV into perspective by comparing it with the lower V-coverage risk associated with MMR + V. METHODS: FC and varicella burdens were measured by total numbers or duration of hospitalisations. A model, based on several assumptions and integrating parameters from heterogeneous data sources relevant to Germany, was developed to evaluate hospitalisation ratios (HRs; ratios between yearly numbers of varicella-related hospitalisation days prevented by MMRV and yearly numbers of FC-related hospitalisation days attributed to MMRV, both compared with MMR + V). A sensitivity analysis estimated HR under different scenarios beyond the German experience. RESULTS: For parameter values compatible with the German experience, where MMRV (Priorix-Tetra™, GSK, Belgium) was introduced in 2006, the model predicted that transitioning from MMR + V to MMRV would induce 225 vaccine-related FC hospitalisation days whilst preventing 1976 varicella-related hospitalisation days per year. The HR estimated by Monte Carlo simulations was 8.5 (95 % confidence interval: 1.99–25.22). A sensitivity analysis on two key parameters suggested that transitioning from MMR + V to MMRV would be favourable in situations where MMRV use would significantly impact varicella vaccination uptake. CONCLUSIONS: MMRV use instead of MMR + V can substantially reduce the number of hospitalisation days, despite increased FC risk when MMRV is used as a first dose of measles-containing vaccine.