RESUMEN
OBJECTIVE: To analyze COVID-19 vaccine uptake in children and to investigate factors associated with two outcomes variables: (a) not even beginning; (b) not completing the COVID-19 vaccine series. METHODS: We used data of children aged 6-7 years from the 2015 Pelotas c Birth Cohort Study. COVID-19 vaccination status was collected from immunization cards and National Immunization Program Information System. Adjusted analyses were performed using a hierarchical model to identify factors associated with the two study outcomes. RESULTS: Among 3867 children, 20.7 % (95 % CI, 19.5 %-22.0 %) did not even begin the 2-dose primary COVID-19 vaccine series, and 28.2 % (95 % CI, 26.6 %-29.8 %) did not complete the series with the second dose. Children not even beginning the COVID-19 vaccine series were more likely to have a White mother, not to have obesity, to have a history of COVID-19 infection, to have received non-recommended drugs for COVID-19, to be afraid of needles, and to have an incomplete diphtheria-tetanus-pertussis (DTP) and poliovirus immunization schedule. Not completing the 2-dose series was associated with lower maternal age and education, mother's self-identification as White or Brown, lower household income, lack of access to health services, not having completed the DTP and poliovirus immunization schedule and living with a person with a history of infection with COVID-19. CONCLUSION: The results highlight a vaccine-hesitant parents' group who chose not beginning the COVID-19 vaccine series of their children and, another group of parents who failure to complete the child's series due to difficulty accessing health services.