OBJECTIVE: Although vaccination confidence is declining globally, there is little detailed information from low- and middle-income countries about factors influencing routine vaccination behavior in these contexts. METHODS: In mid-2022, we surveyed people who gave birth in Kenya between 2017-2022, and asked them about their childrens vaccination history and about hypothesized correlates of vaccination per the Behavioural and Social Drivers of Vaccination model. RESULTS: Of 873 children in this sample, 117 (13%) were under-vaccinated (i.e., delayed or missing vaccine dose(s)) - and under-vaccination was more common among births during the COVID-19 pandemic (2020-2022) versus pre-pandemic (2017-2019). In multi-level multivariable models, children of respondents who expressed concerns about serious side effects from vaccines had significantly higher odds of missed vaccine dose(s) (aOR 2.06, 95 % CI 1.14-3.72), and there was a strong association between having more safety concerns now versus before the COVID-19 pandemic (aOR missed dose(s) 4.44, 95 % CI 1.71-11.51; aOR under-vaccination 3.03, 95 % CI 1.28-7.19). People with greater trust in health workers had lower odds of having a child with missed vaccine dose(s) (aOR 0.85, 95 % CI 0.75-0.97). People who reported higher patient-centered quality of vaccination care had much lower odds of having children with delayed or missed vaccine dose(s) (aOR missed dose(s) 0.14, 95 % CI 0.04-0.58; aOR under-vaccination 0.27, 95 % CI 0.10-0.79). CONCLUSIONS: These findings highlight potential strategies to improve vaccine coverage: greater focus on patient-centered quality of care, training healthcare workers on how to address safety concerns about vaccines, and building trust in the health care system and in health workers.