Editorial Board:
Editor:
George H. Conklin,
 North Carolina
 Central University

Board:
Bob Davis,
 North Carolina
 Agricultural and
 Technical State
 University

Richard Dixon,
 UNC-Wilmington

Ken Land,
 Duke University

Miles Simpson,
 North Carolina
 Central University

Ron Wimberley,
 N.C. State University

Robert Wortham,
 North Carolina
 Central University

Editorial Assistants

Rob Tolliver,
 Duke University

Shannon O'Connor,
 North Carolina
 Central University

John W.M. Russell,
 Technical
 Consultant

® 

Volume 6, Number 1
Spring 2008

Predictive Factors of Disparities in Childhood Immunization Services:
Some Evidence from Southern United States

by

Roger Yao Klomegah

Fayetteville State University 

    Disease prevention through immunization has been a top priority of health care providers as evidenced in the 1977 policy statement of the American Academy of Pediatrics (AAP) - a policy that called for immunization of all children (American Academy of Pediatrics, 1977). Over the years, the entire staff of the health care delivery system, including pediatricians, family physicians, and nurses have been given the mandate to protect children from preventable diseases and the responsibility to make sure that every child is immunized (Kohrt, 2003). Consequently, more children received more vaccines than ever before, up to 23 injections for 11 different diseases, most of which are given in primary care settings (Kohrt, 2003).

    Recently, the National Vaccine Advisory Committee (NVAC) presented a revised form of "Standard for Child and Adolescent Immunization Practices." The American Academy of Pediatrics (AAP) also released a policy statement titled “Increasing Immunization Coverage” issued by the committee on Community Health Services and the committee on Practice and Ambulatory Medicine (National Vaccine Advisory Committee, 2003; American Academy of Pediatrics, 2003). These releases contain recommendations for primary care practitioners for improving the quality of immunization services and offer them opportunities to do better, but for them to do better, they first need to know how they are doing (Kohrt, 2003).

    The new 2003 recommendations provide the opportunity for health care providers to improve the practice's preventive care system. Among the NVAC's standards and AAP recommendations are the following:

a) Ensuring children access to immunization with limited costs to families.

b) Assessment of immunization rates at least once every 3 to 4 years. Assessment of the vaccine status of every child at every visit – summary of immunization given by all providers. Participation in an immunization registry is encouraged.

c) The following need to have written protocols developed and taught to all staff and reviewed regularly. 

• Reminder/recall tools to be used by staff
• VIS protocol are followed
• Vaccine protocols are accessible
• Documentation protocols are developed so that all vaccines and immunizations are documented
• Storage and handling guidelines are easily accessible
• Reimbursement protocols are put in place for efficient fee billing

    In order for primary care practices to be efficient and effective, it is expected that NVAC "Standards for Children and Adolescent Immunization Practices" and the AAP policy statements are translated into actionable systems and practice tools, which many primary care systems have done. However, there are challenges both in and outside the health care delivery practice such as racial, geographic variations, lack of vaccines, and parental level of education. Moreover, it has been documented that inequities in health care and health outcomes exist among racial and ethnic minorities in the United States; practices vary from state to state, region to region, community to community, rural to urban areas, etc. (Larson, 2003).

    The afore-mentioned challenges warrant the current research. The objective of the current study is to examine some factors that relate to disparities in childhood immunization services offered to children and their mothers in the southern states of the United States using the 2003 National Immunization Survey (NIS) data. Specifically, the study looks at how the probability of disparities in services offered to children relate to socio-demographic factors. The services in question are adequate provider data, comprehensive care; acute illness care; follow-up visits; after-hours telephone coverage; Women, Infants, and Children (WIC) programs; report of vaccinations to registry; and provider's participation in Vaccines For Children (VFC) program. The explanatory factors in study include racial/ethnic minority groups because they are the fastest growing segments of the population and their health issues will have implications for society. Moreover, immunization which is one of the 10 leading health indicators of a nation's health, has been a major concern for the U.S. and rightly so, because health disparities is a function of childhood immunization. 

    The research question being addressed is: what are the predictors of differential services offered by health care providers to children with regards to the following: visits by health care providers, after-hours telephone coverage, WIC programs, reporting of vaccinations to registry, and provider participation in Vaccines For Children (VFC) program?

    In order to address the nation's health adequately, it is important to understand the health indicators and their demographic, social, and economic correlates. Comprehension of these dynamics could lead to the development of viable strategies and interventions that may address health disparities among the diverse segments of the population.

    In 2000, since there was no existing research on disparities in childhood immunization in the state of North Carolina, the Department of Health and Human Services established a "Disparities Core Team" to address the issue (Flynn-Saldana, 2003). Toward this end, the Disparities Core Team undertook a kindergarten survey to examine the existence of disparities. Eighty one schools were included in the sample and from that, a systematic random sample of 30 children were selected from the kindergarten class roster (Flynn-Saldana, 2003). The following information were gathered from school records: school name, school district, urbanicity, child date of birth, gender, mother's race and ethnicity, primary site of health care, and dates of immunization. Data were analyzed based on the 4:3:1 series, (that is, 4 doses of Diphtheria, Tetanus, and Pertusis; 3 doses of Polio; and 1 dose of Measles, Mumps, and Rubella). (Flynn-Saldana, 2003: 107).

    On the whole, the statewide immunization rate at 24 months for the sample was 76%. White children were more likely to be up to date by 24 months than African American, Latino, and Asian children. However, there were no variations among children on the basis of urbanicity, gender, or region in the state (Flynn-Saldana, 2003). When immunization coverage rates were compared along racial/ethnicity lines based on the two categories of healthcare (regular and private sites), white children are more likely to be up to date than Latino children among children identifying health departments as regular healthcare site, and also, white children are more likely to be up to date on immunization than African American and Latino children among children who identified their health departments as private providers (Flynn-Saldana, 2003). Some regional variations were also discovered. For example, children living in rural areas in Region 1 (Westmost area), Region 2 (Mountains), and Region 5 (Raleigh-Durham area) were more likely to be up to date than children living in rural areas in Region 6 (Fayetteville/Wilmington area) (Flynn-Saldana, 2003). 

    Despite the availability of safe and effective vaccines and significant improvement in the reduction in vaccine-preventable diseases, the delivery to and acceptance of vaccinations by targeted populations still face some challenges. The complexity of vaccination schedules make delivery of appropriate vaccines in a timely fashion increasingly problematic for the health care delivery system and its staff. Consequently, a Task Force on Community Preventive Services with the support of the Centers for Disease Control and Prevention (CDC) released recommendations regarding intervention programs to guide communities to increase levels of immunization coverage and decrease vaccine-preventable diseases. Some of the recommendations are discussed below. 

    Home visit is one of the recommendations for improving community demand for vaccinations. It involves providing face-to-face services to clients in the various homes. Among the services offered are education, assessment of need, referral, and vaccinations. Home visitation may also include telephone and/or mail reminders. Available studies show that home visit interventions improve vaccination coverage among socioeconomically disadvantaged populations (Center of Disease Control and Prevention, 1999).

    A strongly recommended approach to increasing community demand for vaccinations is client reminder/recall programs (Center of Disease Control and Prevention, 1999). This program involves reminding members of a target population that vaccinations are due (reminders) or late (recall). Reminders can be delivered by a variety of means such as telephone, mail, and postcard (Center of Disease Control and Prevention, 1999). It has been noted that reminder/recall interventions improves vaccination coverage in both children and adults and in a different populations (Center of Disease Control and Prevention, 1999).

    A closely related recommendation is provider reminder/recall interventions that inform administrators of vaccinations which individual clients are due (reminder) or overdue (recall) for specific vaccinations. Reminders are delivered by a variety of techniques such as client charts, computers, mail, etc. There is evidence to show that provider reminders improve vaccination coverage in children, adolescents, and adults (Center of Disease Control and Prevention, 1999). 

    Another recommendation for increasing community demand for vaccinations is provision of incentives for clients and families. Client incentives involve the providing financial or other incentives to persons in order to motivate them to accept vaccinations. Incentives could be either rewards or penalties. Examples are Women, Infants, and Children (WIC) programs and childcare, school, and college attendance requirements (Center of Disease Control and Prevention, 1999).  Unfortunately, insufficient evidence exists to assess the effectiveness of client incentives in improving immunization coverage (Center of Disease Control and Prevention, 1999).

    Solberg and others (1997) have suggested that health care providers need to increase their attempts to recommend and provide preventive services to all patients. Clients of 22 private care clinics in Minneapolis in Minnesota were surveyed to measure their self-reported need for the 8 targeted preventive services. Information was elicited about when the respondents last received each of the targeted services and whether the service was recommended or provided. Of the low socioeconomic group, 35% had medical assistance, 39% had no insurance, 10% were on Medicare, and 17% of them had other insurances. In the high socioeconomic group, 1.5% of them were on Medicare and the rest had other insurance. Solberg and others (1997) found out that while the low-socioeconomic group was likely to receive recommendations for need preventive services, the rates of recommendation in both groups needed improvement because only 7 to 10 percent of patients who needed a service receive recommendation during a clinic visit. However, people with low-socioeconomic status received advice to quit tobacco use and got more frequent service to that effect. The need for preventive services was great for low-socioeconomic patients. For example, they were 20 to 30 percent less up-to-date on target preventive services such as mammograms and cholesterol screenings.

    The above information illustrates the limited target preventive services available to patients of low-socioeconomic status in Minneapolis, a point that underscores the importance of improving the preventive services delivery system, especially child vaccinations (immunizations) as well as assessing the practices of providers.

    A major cause of death among persons aged 65 and over in the United States is influenza and pneumococcal diseases and substantial racial/ethnic disparities in adult vaccination against these diseases have been documented in a national survey. In 2000, vaccination coverage levels among Blacks and Hispanics were 31% and 30% respectively, compared with 57% for Whites. Persons most likely to be vaccinated are persons with the highest education level and persons with frequent visits to health care providers (Centers for Disease Control and Prevention, 2003). These findings indicate the persistence of inequity in health care delivery by race and ethnicity.

    From the time they are born, babies are confronted with a variety of challenges to their immune system. Their intestines encounter foreign proteins in milk and formula they drink, their lungs inhale bacteria on the surface of dust in the air, and thousands of bacteria start to invade their skin, the lining of the nose, throat, and intestines. In fact, babies, infants, and children frequently encounter viruses and bacteria in many places in their bodies everyday. Nonetheless, they survive because we are capable of meeting these challenges, and one way we do that is through immunization – the immune response to bacteria in many places of their bodies (Offit, 2000).  However, the delivery of this health care service is without its challenges. It has been recognized that inequities in health care and health outcomes exist among racial and ethnic minorities in the United States.

    One of the goals of Healthy People 2010 was to eliminate health disparities and defined immunization rates as one of the health indicators of whether the goal has been met or not (US Department of Health & Human Services, 2001). Disparities in health care have been associated with a variety of demographic factors such as gender, race and ethnicity, geographic location, and disabilities, but these factors alone cannot explain disparities. Disparities are believed to be a complex interplay among biological, social, health behaviors and practices, and policies and interventions (Larson, 2003).

    The Institute of Medicine, in 2002, released a report demonstrating that minorities receive substandard health care for a number of health conditions and have poorer health outcomes. For example, infant death rate for African Americans and Native Americans is twice that of Whites, and Hispanics have higher rates of tuberculosis and hypertension than do Whites (Larson, 2003).

    Potential explanations for disparities in immunization rates are categorized as 
a) structural problems that relate to the system of care and 
b) process problems that relate to the characteristics of provider and the patient and interactions between them (Larson, 2003). 

    Structural barriers to adequate immunization include language, lack of health insurance, socioeconomic status, education, income, childcare, work demand, and transportation, or geographic distance from providers. Process barriers have been identified as patient preferences, distrust of "the system," and lack of knowledge (Larson, 2003). For example, certain racial and ethnic minorities may prefer to seek help and advice from religious or lay healers rather than from physicians. Some members of minority groups also prefer providers from their own racial/ethnic background and such providers may not be available (Larson, 2003). There are three possible provider characteristics that may result in disparities in health care. These are 

1. bias, 
2. clinical uncertainty among providers about how to interact with minorities, and 
3. the provider's beliefs or stereotypes regarding the behavior or health of minorities (Larson, 2003).

    From the literature, the following hypothesis was posited for verification: 

Controlling for the influence of race/ethnicity, socio-demographic factors (age, gender, education, marital status, and income) account for disparities in immunization services and practices offered to children and their mothers. 

    The study data source is the 2003 National Immunization Survey (NIS). The 2003 NIS public-use data file was utilized for analysis. The NIS is sponsored by The National Immunization Program (NIP) and conducted jointly by NIP and National Center for Health Statistics (NCHS), Centers for Disease Control and Prevention (CDC). The NIS is a list-assisted random-digit-dialing telephone survey followed by mailed survey that began data collection in April 1994 to monitor childhood immunization.

    The target population for the NIS is children between the ages of 19 and 35 months living in households in the U.S. at the time of interview. The official coverage estimates reported from the survey are rates of being up-to-date with regard to the recommended numbers of doses of all recommended vaccines (CDC 2003). 

    For the 2003 NIS, a total of about 3.7 million telephone numbers yielded household interviews for 30,930 children, and 21, 310 of whom had provided data that were adequate to determine whether the child was up-to-date in terms of the recommended immunization schedule (NIS, 2004).  For the purpose of this study, only respondents living in the southern states were selected for analysis. The U.S. Bureau of Census groups the 50 states and the District of Columbia for statistical purposes into four geographic regions—Northeast, Midwest, South, and West, based on proximity (Health United States, 2004). The states in the South division and involved in this study are Arkansas,  District of Columbia, Delaware, West Virginia, Virginia, Kentucky, Louisiana, Tennessee, North Carolina, South Carolina, Mississippi, Alabama, Georgia, and Florida. This selection yielded a sample size of approximately 7,128.

    Variables involved in this study are as follows:

Predictor variables are age of mother, age of child, gender of child, mother's educational level, marital status, and family income. 

Dependent variables are provider services, namely, adequate provider data, comprehensive care, acute illness care, follow-up visits, after-hours telephone coverage, participation in WIC benefits program/service, report vaccination to immunization registry, and provider's participation in VFC program. 

    The dependent variables were operationalized as "Yes" or "No" responses to questions as to whether the above-mentioned services were offered to child.  Control variables are racial/ethnic categories, which are Hispanic, White, Black, and Other/Mixed. 

    Tabular analysis was used to summarize and compare sample responses.  Contingency tables were created to describe association between racial/ethnic categories and background characteristics of respondents as well as provider services. In addition, multivariate logistic regression was employed to assess the predictive power of each socio-demographic variable relative to the reported immunization services offered to children while controlling for the influence of racial/ethnic categories.

    There is no direct measure of race/ethnicity of respondent (mother) and therefore, race/ethnicity category of child was used as a proxy for race/ethnicity of mother. The problem with this is, a mother may be of a particular race and have a biracial baby, and therefore using the child's race as a proxy for mother's race/ethnicity may not necessarily reflect the true racial/ethnic category of the mother.   Secondly, the fourth racial category (other/mixed) in the study could be misleading since Asians, Native Americans, and biracial respondents might be grouped together.

    A little over half of respondents (55%) were 30 years and more, 42.2% were between 20-29 years old, and 3% were below 19 years of age. Forty-two percent of mothers included in the study have college education and the rest have non college formal education. The majority of respondents (71%) were married, and the racial/ethnic distribution of respondents are as follows: White (56%), Black (23%), Hispanic (15%), and other or mixed (6.2%).

Background Characteristics

    As summarized in Table 1, Whites are overrepresented in the 30+ age group (62%) and Blacks are overrepresented in the 20-29 age group (51%) as well as the youngest age category (<= 19) (6%). There are virtually no differences among the distribution of age groups of children.  Whites (52%) and Other/Mixed race (52%) respondents have higher education than do the other racial groups. At the other end of the spectrum, more Hispanics (32%) have less than 12 years of formal education than the other racial categories. With regard to respondents’ marital status, there are more married Whites (85%) than the other racial categories. The opposite is true for Black racial group (62%). For family income, Whites (64%) are found in the high income category and Blacks (39%) are overrepresented in the low income category. Similar pattern can be seen with regards to poverty level.

   Presented in Table 2 is a summary of the association between racial categories and provider services. The majority of all racial categories report that health care providers offer the various services except for WIC benefit program and Report of Vaccination to Immunization registry, about which majority of racial groups report otherwise. 

    Eight different provider services were regressed on the following covariates: age category of child, age category of mother, gender of child, education of mother, marital status of mother, family income, and racial/ethnic categories resulting in 8 models, which are presented in Tables 3A and B. 

    Each model corresponds with a provider service. The names of provider services are replaced by abbreviated letters (due to lack of space) as shown in Tables 3A and B and should be read as follows: APD = adequate provider data (model 1), CC = comprehensive care (model 2), AIC = acute illness care (model 3), FV = follow-up visits (model 4), APC = after-hours phone call (model 5), WIC = women, infants and children benefits program (model 6), RR = report vaccination to immunization registry (model 7), VFC = provider enrolls in vaccination for children program (model 8).

    As seen in model 1, racial category and family income are significant predictors of immunization services offered to children. Immunization providers are 1.4 times more likely to have adequate data for White children than for Hispanic children. Mothers in high income group are less likely than others to have providers keep adequate data on their children (odds ratio = .83).

    In model 2, racial/ethnic category has no predictive power in terms of a provider offering comprehensive care to a child. Rather, age category of a child and age category of a mother are significant predictors relative to comprehensive care. In fact, providers are more likely to offer comprehensive care to children of mothers aged 20-29 and 30+, but .69 less likely to offer comprehensive care to child children aged 30-35 months.

    In model 3, racial category and family income are significant predictors of whether an immunization service provider will offer acute illness care to a child. Children of Whites are 1.3 times more likely than children of Hispanics to be provided acute illness care, whereas Black children are far less likely than Hispanic children and children of other racial categories to be offered acute illness care. Children that are 30-35 months old are less likely (odds ratio = .79) to be offered acute illness care than their younger counterparts (19-23 months).  Family income is the strongest predictor of acute illness care offered to children. The odds for children of mothers in high income group to have acute illness care are 1½ times higher than children of low income mothers.

    The data in model 4 show that the only statistically significant predictor of follow-up visits by immunization providers is age category of children. For those children 30-35 age group, the odds for providers doing follow-up visits after immunization is .82 less likely than for children 19-23 age group.

    Model 5 shows that race is a significant predictor of after-hours phone calls to mothers of immunized children and Whites are 1.2 times more likely than Hispanics to receive after-hours phone calls from providers. The odds ratio for children age 30-35 months is .81 meaning that it is less likely for mothers of that age group than mothers of age 19-23 to get after-hours phone calls. Mother's education is also an important predictor factor in after-hours phone call. The higher educated the mother is, the more likely she will receive after-hour phone calls from service providers than if a mother has less than 12 years of education (odds ratio = 1.31). The strongest predictor of after-hours phone call is family income. The odds ratio of mothers in high income category is 1.44 indicating that mothers in high income group are almost 1½ times more likely than those in low income group to receive after-hours phone calls from immunization service providers.

    In model 6, race, age of mother, education, and family income are significant variables in predicting disparity in offering WIC benefits program to children. White women and women of mixed race are less likely to receive WIC benefits than Hispanic women. Similar observation applies to women who are 30 years old and more, women with college level education, and middle and higher income. 

    In model 7, racial category, women's education, and family income are significant predictors of whether or not a provider reports child's vaccination to immunization registry. Racial category has the strongest predictive power. Being black significantly increases the odds (by 1.6 times) of providers reporting children's vaccination to immunization registry compared with being Hispanic. Women with more than 12 years of education are less likely to have their children's providers report vaccination to immunization registry than those with less than 12 years of education. Women from high and middle income families are less likely than women from low income family to have providers report their children's vaccination to immunization registry. 

    As summarized in model 8, the probability of a provider enrolling in vaccination for children program is significantly associated with race, mother's education, and family income. Being of mixed/other race significantly reduces the odds of a child's provider enrolling in vaccination for children program (odds ratio = .64) than being a Hispanic.  Being a mother with more than 12 years of education reduces the likelihood of a provider enrolling in vaccination for children program than mothers with less that 12 years education. Also, coming from middle and high income categories significantly reduces the odds of a provider enrolling in the program than those found in low income category. 

    Based on the above evidence the hypothesis, controlling for the influence of race/ethnicity, socio-demographic factors (age, gender, education, marital status, and income) account for disparities in immunization services offered to women and children, is partially supported. Mother's education, family income, and racial/ethnic categories are important predictors of immunization services disparities in southern United States.

    Over the years, childhood immunization has been a top priority of health care providers. But as has been noted in the introduction, there are challenges to adequate and equitably health care delivery services. These challenges are a function of a complex interplay of several factors including race/ethnicity, gender, education, geographic location, disabilities, biology, behavior and practices, policies and interventions. From the literature, there is enough evidence to suggest disparities in provider services to different racial/ethnic groups in the United States. The findings of current study are no exception and have provided additional data to existing literature.

    The study sets out to examine the predictive powers of a range of socio-demographic covariates on disparities in immunization services. The findings enhance our understanding of the social correlates of differential immunization service delivery. The literature informed us that the CDC recommended the provision of incentives such as WIC benefits for clients and families in order to motivate acceptance of childhood vaccinations (Center of Diseases Control and Prevention, 1999). In congruence with this recommendation, this study has shown that Hispanics (44%) and Blacks (44%) have been offered WIC benefits compared with Whites (29%) and people of mixed race (33%). In fact, as evidenced in a multivariate context, the odds for Whites and people of mixed race being offered WIC benefits decrease by .79 and .76 respectively. The effectiveness of client incentives such as WIC benefits in enhancing immunization coverage needs to be looked into.

    The most important predictors of differential immunization services in the current study are educational level of mothers, family income and race/ethnicity. Educational level of mothers is an important variable, especially in explaining after-hours phone calls to clients by providers. Mothers with more than 12 years of education do receive phone calls from providers. As a matter of fact, educated and well-informed mothers may ensure that necessary immunization services are provided to their children. This finding corroborates earlier findings; for example, Luman and others (2003) used 2001 NIS data to study maternal characteristics associated with vaccination of children and found that mothers with less education are at highest risk of having their child undervaccinated, a situation which may also apply to related services. The association of family income with participation in immunization registry can be explained by the fact that participation is voluntary for both providers and parents. A parent or guardian of a child who is eligible to participate in the registry can refuse participation, and therefore the registry may no longer update nor make the child data available (Department of Public Health, 2007). High and middle income women may not be interested in benefits and services and would rather be more concern with their children's privacy than their counterparts from lower income group. Hence they are less likely than women from low income family to have providers report their children's vaccination to immunization registry. As mentioned in the explanatory framework above, structural barriers to adequate immunization services include education and income, among other factors. In reference to racial/ethnic category, the current data are consistent with past findings to reiterate immunization inequities. Generally, Whites have an edge over other racial/ethnic categories in receiving immunization services in the region under study. 

    To conclude, differential immunization services in the southern states are a truism and cannot be overemphasized. Relative to the above is the fact that education of mothers, family income, and race/ethnicity make a difference in provider services and herein lays the policy implication of the findings – the importance of formal education beyond K-12, as it helps in comprehending the dangers new-born babies are confronted with, a variety of challenges to their immune system. As explained in the framework, new born babies’ intestines encounter foreign proteins in milk and formula they drink; their lungs inhale bacteria on the surface of dust in the air, and thousands of bacteria start to invade their skin, the lining of the nose, throat, and intestines. It is only through immunization that they survive. Secondly, the study results show that minority groups are the most disadvantaged when it comes to receiving the services under study and therefore, it behooves those in positions of influence to put mechanisms in place to help reduce the gap in service delivery for racial/ethnic groups. Secondly, the National Vaccine Advisory Committee (NVAC) in 2003 recommended, among other things, that there should be an opportunity for health care providers to improve the practice of preventive care system and to ensure children access to immunization with limited costs to families. Based on the influence of family income in service inequality as evidenced in this study, attention needs to be paid to the NVAC recommendation. Lastly, because the CDC believed that incentives could motivate mothers to have their children immunized, more minorities (Hispanics and Blacks) than Whites have been offered WIC benefits as evidenced in the data. It is, therefore, suggested that future research should examine the efficacy of such client incentives in enhancing immunization coverage.

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