health communication

Immunization series completion coverage among two year old children in the United States has improved greatly over the past decade. In the present study, 60% of poor, inner-city preschool children received four DTP, three polio and one MMR vaccines by 19 months of age, leaving 40% who were late. The desired outcome of childhood immunization interventions has been to increase immunization series completion levels among two year old children. Although it is important to understand the factors affecting lateness during the first year of a child’s life (e.g. are parents initiating and maintaining well-baby care – as measured by timing of DTP 1 and DTP3- at a time when the incidence of childhood diseases such as pertussis and the health consequences are most serious), ultimately, public health practitioners want to understand and intervene on the factors affecting vac cine series completion. For this reason, the discussion here focuses primarily on understanding the determinants of late immunization at 19 months of age for the completion of four DTP, three polio and one MMR vaccines. The Precaution Adoption Process model provides a useful framework for thinking about and interpreting the study’s findings in terms of parents’ mental frameworks and their behavioral stage of readiness to vaccinate their child.

Stage 1: Parental Awareness and Experience with Childhood Diseases

Parents in this study had a general awareness of and some experience with childhood diseases. When given a list of symptoms for whooping cough and measles, most parents could give one or more correct symptoms- perhaps by chance. (See Table 2). However, general awareness of symptoms did not have a significant impact on parental behavior in terms of the timing of their child’s immunization.
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Perhaps this is because, as the model suggests, knowing about childhood diseases either from personal experience or from information provided by a healthcare professional is but a first step in the process of protecting one’s child from the hazard. It is a necessary but not a sufficient condition for ensuring that a parent gets immunizations in a timely manner for their children.

Parents who had a fairly accurate conceptualization of disease transmission, as captured by the factor analysis and labeled the “contagion factor” (see Table 4), were half as likely to be late for DTP3 at 7 months as those who did not share this view. This suggests that a parent’s mental framework- that is, how she thinks about disease transmission, is related to timing of immunization- especially when the conceptualization tends to be accurate.

Stage 2: Acknowledgment of Personal Susceptibility

The model states that beliefs about personal susceptibility facilitate taking a precaution rather than not taking an action. Among those who said their child was susceptible and were late, the logic appeared to be that “anyone can get the disease” and, if they’re “around a lot of kids” this increases the likelihood of exposure. These parents did not link susceptibility to “not getting shots”. Previous studies have shown that perceived susceptibility to illness was inversely related to up-to-date immunization status. Bates et al., (1994) offered a possible explanation for this phenomenon. Mothers who perceived that their children were less susceptible to illness more frequently utilized preventive services -suggesting that mothers who believe that prevention works and obtain regular preventive care also believe that they can keep their children from becoming ill. The findings from the current study would support this explanation- the primary reason parents said their child wasn’t susceptible to whooping cough, was because they were up-to-date with their shots.

Stage 3: Decides to Immunize Child

The Precaution Adoption Model states that parental beliefs regarding immunization play an important role in the decision to get immunization. One set of beliefs examined in this study were those regarding the effectiveness of immunizations. We found that these beliefs cover a range of accurate and inaccurate information – both of which could motivate parents to get shots. For instance, parents who believe that shots are effective because they “treat” a disease, are less likely to be late at DTP1 as those who do not share this belief. If a parent believes that shots “contain medicine” and/or shots can “cure” childhood diseases, then she may be more inclined to get her child immunized. This finding suggests a need for health education regarding the importance of getting a child immunized to protect him/her from serious diseases even though the immunization itself may cause some discomfort.

Likewise, parental beliefs regarding the side effects of immunizations can also affect their immunization decision. We found that these beliefs are grouped into two categories. Parents are able to distinguish severe from minor side effects (see Table 3). Parents who believe that severe side effects are likely to occur after an immunization, are more likely to be late for receiving four DTP, three polio and one MMR vaccines at 19 months. If parents believe that severe adverse consequences are likely to occur, this presents a major barrier to getting the child immunized. At this stage, a parent’s beliefs about barriers to getting immunizations is a determinant of their decision to get their child immunized.
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Stage 4: Gets Immunization

The results of the logistic regression overwhelmingly indicate that having three or more children was the strongest predictor of lateness at all three points in time: 3 months, 7 months and at 19 months of age. This finding is in keeping with the Precaution-Adoption Process Model which states that one of the major determinants of a person actually taking a precautionary action is the “time, effort and resources available considering competing life demands”. Previous studies have shown that birth order and the number of children that a parent has increases the likelihood of being late for immunization. This study produced similar results. The simplest explanation is that, the greater the number of children, the greater the number of demands on the parent’s time and that is the reason they are more likely to be late.

Finally, the Model suggests that reminders to take a preventive action, also play a key role in whether the person actually follows through with her intention. The results of this study showed that parents who reported receiving immunization information from a physician were significantly less likely to be late at 7 months for DTP3. At 19 months the direction of the odds ratio is the same (i.e. less than 1) however the results are not significant. generic cialis uk


There are several important features of this study. First, this study is one of only a few which addresses the beliefs of disadvantaged, inner-city parents and compares their beliefs with their child’s immunization status. Second, understanding parents’ mental frameworks for thinking about childhood diseases, is a unique approach and one that is necessary to the design and implementation of effective communications programs targeting this audience. This study is one of only a few studies to do so in the immunization area. Finally, the use of computer-assisted telephone interviewing (CATI) is both a strength and a weakness. CATI systems facilitate accuracy in the management of the sample and reduce the number of interviewer errors-for instance, missing a skip pattern. However, using telephone interviews as a means of collecting data from a low-income population is also problematic. As Figure 1 illustrates, 33% of the total sample had a telephone that was either disconnected, not working or was a wrong number. Making contact with individuals who may not be able to afford telephone service on a consistent basis or who may be highly mobile is very difficult. Although telephone surveys have these obvious limitations, the alternatives – mail surveys or face-to-face interviews at an individual’s home also have significant drawbacks.

Potential limitations of this study are as follows. The first limitation of this study is the age of the data. The telephone survey was completed in late 1996 and the medical record review was completed in 1997. However, given that there have been so few studies that have addressed the beliefs of disadvantaged, inner-city parents and fewer still that compare parental beUefs with immunization status, the authors believe the findings are still relevant. A second limitation is the response rate, which was modest and raises the issue of non-response bias. It is impossible to know to what extent, if any, the non-respondents differ with regard to their knowledge, attitudes, beliefs and immunization status. Generalizations from our study are obviously limited to the survey’s target population: low income, inner-city parents of preschool children. A third limitation was that the interview was conducted with the parent after the child had already received the vaccinations that were evaluated. However, it seems reasonable to assume that parental knowledge about and attitudes toward immunization would become more informed and realistic with experience over time, and, perhaps, less likely to stand out as predictors of lateness. Therefore the factors that were associated with late immunization in this study are probably good predictors of lateness in this population. Finally, the odds ratios for some significant factors were large due to small sample size so the results should be viewed with some caution.
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