Determinants of measles-rubella second dose vaccine uptake among children in Mathare informal settlement, Nairobi, Kenya: a mixed-methods study

Abstract

Introduction: measles-rubella remains a major public health concern, with vaccination as the most effective preventive strategy. Despite the introduction of the measles-rubella second dose (MR-2) vaccine to improve immunity, uptake in informal settlements like Mathare, Nairobi, remains suboptimal. This study assessed determinants of MR-2 uptake among children aged 18-59 months in Mathare. Methods: this cross-sectional analytical study used a convergent mixed methods design. Quantitative data were collected through structured household surveys, while qualitative insights were obtained from Key Informant Interviews and Focus Group Discussions. Results: a total of 370 caregivers responded (103% of the targeted 359). MR-2 coverage was 84%, 14% lower than the measles-rubella first dose (MR-1). Uptake was significantly associated with religion, education level, ward of residence, place of delivery, immunization site, and previous unsuccessful vaccination attempts (p < 0.05). Caregivers unaware of the MR-2 schedule were over four times more likely to miss the dose (OR = 4.146, p < 0.001), as well as those who had previously failed to access services (OR = 4.215, p = 0.007). Lack of a vaccination card (OR = 0.314, p = 0.015) and poor schedule knowledge (OR = 0.322, p = 0.014) were also key predictors. Children in Kiamaiko ward (OR = 5.421) and Ngei ward (OR = 4.281) had higher odds of MR-2 uptake compared to Mlango Kubwa ward. Qualitative findings highlighted barriers such as low awareness, misinformation, economic hardship, and health system gaps. Conclusion: improving MR-2 uptake requires enhanced health education, mobile reminders, consistent vaccine supply, extended clinic hours, and targeted outreach.