Trends and Predictors of Measles Immunisation Inequalities Among Children Aged 12-23 Months in the Philippines, 2008-2022

IntroductionThe Philippines continues to experience measles outbreaks with declining coverage of the first dose of the measles vaccine (MCV1). Despite various interventions and policies to improve MCV1 coverage, inequalities persist, influenced by various socio-demographic factors. This study aims to identify predictors and examine trends in socio-economic inequalities in MCV1 receipt. MethodsUsing the four most recent Philippine DHS datasets (2008, 2013, 2017, and 2022), we identified predictors of MCV1 receipt through bivariate and multivariable regression models. We examined trends in socio-economic inequalities in MCV1 using the Slope Index of Inequality (SII) and Relative Index of Inequality (RII). ResultsOur study included 5,584 children aged 12-23 months. Overall MCV1 coverage declined from 84.7% (2008) to 80.8% (2022). Significant predictors of MCV1 receipt included household wealth quintile, maternal education, parity, ANC visits, distance to health facility, and maternal smoking status. Socio-economic inequalities in MCV1 decreased from 2008 (SII=0.27; RII=1.41) to 2013 (SII=0.23; RII=1.33), stagnated in 2017 (SII=0.23; RII=1.35), and increased markedly by 2022 (SII=0.31; RII=1.52). Health system constraints including inadequate vaccine supply, suboptimal cold chain infrastructure, and limited trained immunisation staff disproportionately affected disadvantaged communities. The 2017 Dengvaxia controversy has eroded public trust in vaccines, while recurrent measles outbreaks and the COVID-19 pandemic further disrupted vaccine access. ConclusionSustaining and monitoring equity-focused interventions, strengthening primary healthcare through Universal Health Coverage, and rebuilding community trust and engagement are essential to ensure measles vaccines remain available, accessible, and acceptable to disadvantaged communities experiencing measles outbreaks and immunisation inequalities.