OBJECTIVES: Varicella complications place a large burden on healthcare resources, however, varicella is preventable by mass vaccination with MMRV. The impact on complications of three MMRV programs were explored. METHODS: An age-structured dynamic model compared natural and breakthrough varicella following mass vaccination, to current cases. Age-specific complication rates (neurologic, cutaneous, pulmonary, other) were applied per case. MMRV replaced 80% of MMR over 1 year (basecase) compared to 100% of MMR with a catch-up in 11-13 year-olds (‘catch up’). In an ‘optimal’ scenario, MMR coverage increased from 90% to 95% (1st dose) and 60% to 90% (2nd dose), MMRV replaced 100% MMR within 1 year with a catch-up in 10 year-olds.  RESULTS: MMRV decreased varicella incidence and caused an age shift, however, many post-vaccination cases were breakthrough cases, believed to be milder and require less resource use. Prior to MMRV: highest varicella incidence (per million-person-years of total population) was among 1-4 year-olds (7,482 cases), with 355 complications (age-specific complication rate: 4.75%). Basecase: highest incidence among 10-14 year-olds (907 natural, 633 breakthrough), with 54 complications (age-specific rate: 3.53%); 85% lower versus 1-4 year-olds. ‘Catch-up’: highest incidence among 15-24 year-olds (161 natural, 398 breakthrough), with 49 complications (age-specific rate: 8.82%); 86% lower versus 1-4 year-olds. ‘Optimal’: highest incidence among 15-24 year-olds (22 natural, 80 breakthrough), with 9 complications; 97.5% lower versus 1-4 year-olds. Assuming breakthrough cases have 10% of complications of natural cases, the incidence in the basecase, catch-up and optimal scenarios becomes: 34, 18 and 3 complications respectively. Despite greater risks of complications in older age groups, the reduction in varicella cases significantly reduced the incidence of complications. The ICER remained below €16,000 (direct costs). CONCLUSIONS: Mass varicella vaccination is predicted to significantly reduce varicella and complication cases. As many vaccine era cases will be breakthrough; burden to patients and healthcare systems may be reduced further.