Vaccine coverage within the first year of life and associated factors with incomplete immunization in a Brazilian birth cohort

Background: Immunization has been held as a major achievement for global health, however, still exist many children who are not completely vaccinated. Knowledge about factors contributing to the incomplete immunization is important to develop effective strategies and interventions to achieve universal coverage to control or eradicate vaccine-preventable diseases. This study aimed to describe immunization coverage within the first year of life and associated factors with incompleteness among participants of the 2015 Pelotas Birth Cohort, Brazil.

Methods: Cross-sectional analyses were performed using data from a population-based cohort. Information on vaccination status was collected from immunization cards and verbal mother's reports from 4014 children aged 24 months. Coverage was described for each vaccine, for the basic and the complete national schedule. Incomplete vaccination was defined as failure to receive the recommended number of doses by the National Immunization Program in 2015. Bivariate and multivariate Poisson regressions with robust variance were conducted to identify factors associated with incompleteness.

Results: Vaccine coverage of individual vaccines varied from 81% (Hepatitis A) to 97% (BCG). Full immunization coverage were 77% (95% CI: 75.8; 78.4) and 66.1% (95% CI: 64.6; 67.5), for basic and expanded indicators, relatively. Multivariate analyses showed that factors associated with incompleteness (for both basic and expanded coverage) were high family income, high parity, low number of prenatal consultations, not have done the tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine during pregnancy, not have breastfeed the child until at age 12 months and not have used public health care services for child's vaccination.

Conclusion: Findings of our study show the need to develop and implement policies and programs to achieve complete immunization during the first year of life. Some strategies would include an increase in the primary health care services networks, improving their quality and access, the dissemination of scientific-based evidence about the benefits of vaccination, through communication campaigns and guidance provided by health professionals, especially those responsible for prenatal care.