Compliance with the vaccination schedule in the population evaluated in the present study was 52.1%, well below the goal of 95% established by the national immunization program and also below the coverage achieved in infants under 12 months of age in Recife in 2015 with respect to the third dose of the diphtheria-tetanus-acellular pertussis-hepatitis B virus-inactivated poliovirus and Haemophilus influenzae type b (pentavalent DTaP-HB-IPV-Hib) vaccine .
The pentavalent vaccine is considered a good indicator of compliance with the complete vaccination schedule, since it reflects the capacity of the healthcare service to reach the same child and deliver the series of three doses required . The percentage of coverage found in this community is comparable to statistics for countries classified as having medium to low human development indices such as Pakistan, India and Ethiopia. In those countries, the rates of complete vaccine coverage for children of 12 to 23 months of age were 51.3% , 53%  and 58.4% , respectively.
Possible interruptions in the supply of immunobiological agents in healthcare services, particularly with respect to the vaccines most recently included in the immunization schedule, could have interfered with the results obtained, as found in a recent study conducted to analyze the vaccines most recently included in the vaccination schedule . The restriction regarding the child’s age in months and days for application of the oral vaccine against human rotavirus, justified for safety reasons, may also constitute a relevant factor.
The significant reduction in the incidence of vaccine-preventable diseases in recent decades could have changed parents’ perceptions regarding the benefits of vaccinating children in relation to potential adverse events, despite the fact that these are rare . Missing the opportunity to vaccinate children attending a healthcare service for another reason or even when they are just accompanying their mothers also contributes to the low rates of immunization coverage .
An inverse association was found in the present study between compliance with the vaccination schedule and the child’s age. This finding is in agreement with the results of a prospective cohort study conducted in the Brazilian state of Maranhão in which incomplete vaccination increased as a function of the child’s age . A study conducted with hospitalized children in Recife reported similar findings .
This could be attributed to the fact that most of the vaccines included in the vaccination schedule are given in the first year of life, principally up to six months, on dates that coincide with the child’s routine check-up visit. After this age, monitoring at the healthcare unit becomes less frequent and as parents’ attention is diverted to younger siblings, the risk of inadequate vaccination increases in the older age group [5,21].
Nonetheless, in communities in which the Family Health Strategy is in operation, compliance with the vaccination schedule should not be linked exclusively to the child going to the healthcare unit, but should also be associated with monthly home visits by community health agents as part of their attributions in promoting family health within their defined geographical area . Another Family Health Strategy activity that encourages vaccination is actively searching for children who have failed to attend for their vaccination on the scheduled date by ensuring that the control card in the vaccination room is correctly filed and used within an appropriate timeframe and in a programmed manner .
The finding of an association between compliance with the vaccination schedule and maternal education level corroborates various other reports [3,5,7,9,22]. The association between poor maternal schooling and inadequate vaccination can be explained by the fact that education level influences knowledge on the different types of vaccine, why they are necessary, their availability, recommendations, benefits and risks . Nevertheless, there is controversy on the subject, as shown in another state in Brazil where compliance with vaccination was better among the children of relatively uneducated mothers, probably due to their need to maintain the child’s vaccination card up-to-date to ensure continuity of their benefits within the Family Benefit Program .
No association was found between social class, classified according to family income, and compliance with the vaccination schedule, and this could be a consequence of the homogeneity of income in this population, preventing comparisons from being made, since the majority of families belonged to social classes C, D or E. In this respect, a study conducted in the capital cities of the northeastern states of Brazil showed lower rates of vaccination coverage in children belonging to social class A, i.e. those with the highest family income .
No association was found between maternal age and compliance with the child’s vaccination schedule. Nevertheless, a recent publication showed that incomplete vaccination was 26% more common among children of adolescent mothers .
In the results of the present study, no association was found between any of the factors related to maternal prenatal care and compliance with the childhood vaccination schedule. This finding contradicts the results of another study showing that maternal prenatal care initiated only in the third trimester of pregnancy and having attended fewer than six prenatal consultations were factors associated with incomplete childhood vaccination . In the present sample, however, almost all the mothers interviewed had received prenatal care, making comparison between groups impossible.
A limitation of this study is that the evaluation failed to take into account the types of vaccine responsible for the rates of non-compliance, i.e. whether the newer or older vaccines were more likely to be missed. On the other hand, a strongpoint lies in the fact that the data on compliance with vaccination were obtained directly from the child’s personal health record, thus minimizing the possibility of biases that can occur when data are provided verbally. The fact that an evaluation of internal validity was performed represents another strongpoint, since this allows the present findings to be compared with results for the same population in different surveys or indeed for the findings to be extrapolated to a population with similar characteristics.
This was the first study to use an epidemiological approach with non-aggregate data at community level and the results could be proposed as baseline data with which to monitor compliance with the vaccination schedule in this specific population.
The associated factors identified here need to be submitted to a more in-depth analysis by means of a qualitative study focusing on the reasons for non-compliance with the vaccination schedule. Such further evaluation would take into consideration the attitude of the parents or guardians in relation to the child’s vaccination.