Impact of vaccination timing and coverage on measles near elimination dynamics: a mathematical modelling analysis

The Joint Committee for Vaccination and Immunisation recommended to implement an earlier second dose for the Measles-Mumps-Rubella (MMR) vaccine starting in 2026 in the United Kingdom. We investigated the impact of these changes on measles transmission in England. Using an age- and region-stratified mathematical model, we simulated outbreaks with different vaccination schedules and coverage, using electronic health records and outbreak data from 2010 to 2019. Delivering the second MMR dose at 24 months reduced cases by 11.86% (IQR: -3.3; 23.81%) compared to the current schedule (3 years and 4 months) and showed a 22.39% (IQR: 10.05; 32.79%) reduction of cases if achieving the same coverage as the first MMR dose. The effect of delivering an earlier second MMR was lower when waning of vaccine-induced immunity was included (5.28% (-10.92; 19.63%)). Increasing first-dose coverage by 0.5% annually yielded slightly better outcomes than an earlier second dose (14.68% reduction, IQR:1.19; 27.49.9%). While improving first-dose uptake had the greatest impact, it may be difficult to achieve. Thus, an earlier second MMR dose can be a feasible alternative to reduce the measles burden in England where measles transmission follows typical near-elimination dynamics.