Incomplete childhood immunization with new and old vaccines and associated factors: BRISA birth cohort, São Luís, Maranhão State, Northeast Brazil.

This study estimated the percentages of incomplete immunization with new vaccines and old vaccines and associated factors in children 13 to 35 months of age belonging to a birth cohort in São Luís, the capital of Maranhão State, Brazil. The sample was probabilistic, with 3,076 children born in 2010. Information on vaccination was obtained from the Child's Health Card. The new vaccines, namely those introduced in 2010, were meningococcal C and 10-valent pneumococcal, and the old vaccines, or those already on the childhood immunization schedule, were BCG, hepatitis B, human rotavirus, polio, tetravalent (diphtheria, tetanus, pertussis, Haemophilus influenzae b), yellow fever, and triple viral (measles, mumps, rubella). The study used hierarchical modeling and Poisson regression with robust variance. Prevalence ratios (PR) and 95% confidence intervals (95%CI) were calculated. Incomplete immunization was higher with new vaccines (51.1%) than with old vaccines (33.2%). Children 25 to 35 months of age (PR = 1.27; 95%CI: 1.14-1.41) and those in economic classes D/E (PR = 1.20; 95%CI: 1.06-1.35) were only significantly associated with new vaccines; low maternal schooling (PR = 1.58; 95%CI: 1.21-2.06), unavailability of outpatient and/or hospital care for the child (PR = 1.20; 95%CI: 1.04-1.38), and unavailability of the vaccine in health services (PR: 1.28; 95%CI: 1.12-1.46) were only associated with old vaccines. Immunization strategies should consider the vulnerability of older preschool-age children and those belonging to classes D and E, especially when new vaccines are introduced, as well as children of mothers with low schooling. Strategies should also address problems with the availability of health services and vaccines.