Caregiver Socio-Demographic Factors That Influence the Uptake of Third and Fourth Doses of Malaria Vaccine Among Under-Fives in Muhoroni Sub-County, Kenya

Malaria remains a leading cause of morbidity and mortality among children under five in sub-Saharan Africa, accounting for approximately 90% of childhood malaria deaths (WHO, 2023). The RTS, S/AS01E malaria vaccine, administered in four doses at 6, 7, 9, and 24 months, has shown moderate efficacy in reducing clinical and severe malaria (WHO, 2022). Despite promising outcomes, uptake of the third and fourth doses remains suboptimal in Kenya, particularly in high-burden areas such as Muhoroni Sub-County, where coverage drops from 72.1% for the first dose to 31.4% for the fourth dose (Okanda et al., 2023). Understanding sociodemographic factors that influence the poor uptake of third and fourth vaccine to dose uptake is critical for sustaining malaria prevention gains. An analytical cross-sectional study employing mixed methods was conducted among 289 caregivers of children aged 9–60 months who had completed the first two doses of the malaria vaccine in Muhoroni Sub-County. Stratified random sampling was used to select participants. Quantitative data were collected via structured questionnaires and analysed using SPSS v27. Descriptive statistics summarized uptake patterns, while Chi-square tests and logistic regression identified predictors of third and fourth dose uptake at a 95% confidence interval. Qualitative data from key informant interviews were thematically analysed using NVivo software. The uptake of the third dose was 50.9% (n=147), while only 10.4% (n=30) received the fourth dose. Higher caregiver education was significantly associated with third dose uptake (OR=1.27; 95% CI: 0.56–2.89; p=0.043). Greater distance to health facilities reduced the odds of third dose uptake by 81% (OR=0.19; 95% CI: 0.11–0.31; p<0.001). Cultural beliefs discouraging vaccination were negatively associated with uptake of the third dose (χ²=11.17; p=0.001), while the perception that children receive “too many vaccines” was linked to lower fourth dose uptake (χ²=4.17; p=0.041). Qualitative findings reinforced these results, highlighting logistical barriers, misinformation, and limited community engagement as key obstacles. Third and fourth dose uptake of RTS, S/AS01E remains far below WHO targets in Muhoroni Sub-County. Education level, proximity to health services, and socio-cultural perceptions significantly influence uptake. Targeted strategies, including community-driven awareness campaigns, improved vaccine accessibility, and culturally sensitive health messaging, are essential to close the late-dose coverage gap and reduce malaria-related child mortality.