Potential impacts of schedule changes, waning immunity and vaccine uptake on measles elimination in Australia

The second dose of MMR vaccine (MMR2) is scheduled at 4 years in Australia and the USA but earlier in some European countries. We modelled the effect on measles elimination status and population susceptibility of shifting delivery of MMR2 from 4 years to 18 months using relevant Australian data. Susceptibility in young children was reduced but elimination was not sustainable past 2015 if 6% of vaccinated seroconverters became susceptible after 10 years. One-dose MMR coverage of 96% or greater maintained elimination more effectively than modelled changes in scheduling, suggesting that maximising one-dose MMR coverage should be the highest priority.