Exploring relevant features associated with measles nonvaccination using a machine learning approach

Abstract: Measles is resurging around the world, and large outbreaks have been observed in several parts of the world. In 2019 the Philippines suffered a major measles outbreak partly due to low immunization rates in certain parts of the population. There is currently limited research on how to identify and reach pockets of unvaccinated individuals effectively. This thesis aims to find important factors associated with non-vaccination against measles using a machine learning approach, using data from the 2017 Philippine National Demographic and Health Survey. In the analyzed sample (n = 4006), 74.84% of children aged 9 months to 3 years had received their first dose of measles vaccine, and 25.16% had not. Logistic regression with all 536 candidate features was fit with the regularized regression method Elastic Net, capable of automatically selecting relevant features. The final model consists of 32 predictors, and these are related to access and contact with healthcare, the region of residence, wealth, education, religion, ethnicity, sanitary conditions, the ideal number of children, husbands’ occupation, age and weight of the child, and features relating to pre and postnatal care. Total accuracy of the final model is 79.02% [95% confidence interval: (76.37%, 81.5%)], sensitivity: 97.73%, specificity: 23.41% and area under receiver operating characteristic curve: 0.81. The results indicate that socioeconomic differences determine to a degree measles vaccination. However, the difficulty in classifying non-vaccinated children, the low specificity, using only health and demographic characteristics suggests other factors than what is available in the analyzed data, possibly vaccine hesitation, could have a large effect on measles non-vaccination. Based on the results, efforts should be made to ensure access to facility-based delivery for all mothers regardless of socioeconomic status, to improve measles vaccination rates in the Philippines.