Abstract
Objective: We examined pregnant women's intention to obtain the seasonal influenza vaccine via a randomized controlled study examining the effects of immunization history, message exposure, and sociodemographic correlates.
Methods: Pregnant women ages 18–50 participated in a randomized message framing study from September 2011 through May 2012. Venue-based sampling was used to recruit racial and ethnic minority women throughout Atlanta, Georgia. Key outcomes were evaluated using bivariate and multivariate analyses.
Results: History of influenza immunization was positively associated with intent to immunize during pregnancy [OR = 2.31, 90%CI: (1.06, 5.00)]. Significant correlates of intention to immunize included perceived susceptibility to influenza during pregnancy [OR = 3.8, 90% CI: (1.75, 8.36)] and vaccine efficacy [OR = 10.53, 90% CI: (4.34, 25.50)]. Single message exposure did not influence a woman's intent to vaccinate.
Conclusions: Prior immunization, perceived flu susceptibility and perceived vaccine effectiveness promoted immunization intent among this population of pregnant minority women. Vaccine efficacy and disease susceptibility are critical to promoting immunization among women with no history of seasonal influenza immunization, while those who received the vaccine are likely to do so again. These findings provide evidence for the promotion of repeated exposure to vaccine messages emphasizing vaccine efficacy, normative support, and susceptibility to influenza.
Introduction
Despite recommendations that pregnant and expecting women receive the trivalent inactivated influenza vaccine,Citation1-3 racial and ethnic minority groups have significantly lower rates of immunization, as well higher rates of influenza-related deaths and complications, as compared with Whites.Citation4-7 Black/African American as well as Hispanic pregnant women and infants experience a higher burden of morbidity, mortality, and hospitalizations due to influenza.Citation4,Citation8-13 Incidence data from 2010–2011 points to greater influenza-related mortality among Hispanic infants (68 cases per 100,000 population) compared with non-Hispanics (39 cases per 100,000).Citation8,Citation14-16
Despite improvements in access to care (i.e., free vaccinations and free prenatal care), disparities in immunization coverage have not been eliminated. One method that has been studied as a way to change health behavior is message framing, backed by Prospect Theory,Citation17-20 which posits that individuals tend to avoid risks when considering gains and prefer risks when considering losses.Citation21 Thus, successful gain-framed messages promote the benefits of taking a risk (i.e., immunization during pregnancy), while loss-framed messages depict the costs of forgoing risk.Citation22 Studies have found that gain-framed messages are most effective in promoting preventive health behavior such as immunization, compared with loss-framed messages, which are most effective in promoting detection practices such as Pap smears.Citation22-26 To our knowledge, message framing has not been systematically evaluated on maternal and infant immunization outcomes among minority women.Citation27-29
In addition, marketing and communication analyses indicate that individuals are more likely to acquire the product of interest after repeated message exposure.Citation30 While single exposure may draw attention to the product, decision to engage in the proposed behavior comes after a second or third exposure to the message.Citation31 Regular communication with a target population “early, often, and fully”Citation31 establishes trust and builds credibility, in addition to fostering a positive attitude toward the proposed behavior or product. In order to promote immunization among women with no history of seasonal influenza immunization, single message exposure is expected to be less effective than repeated exposure to vaccine promotion messages.
Results
Overall, most women reported that they were unlikely to obtain influenza immunization (74.1%, n = 186) and a smaller proportion (25.9%, n = 65) were likely to obtain it during pregnancy. The study population consisted primarily of Black/African American women (88.8%, n = 221), as well as Hispanic/Latina women (6.8%, n = 17) and Multiracial/other women (4.4%, n = 11). () The majority of participants were between 18 to 25 y old (54.8%, n = 136) and living in lower-income households with total earnings among family members comprising ≤$20,000 per year (68.4%, n = 162). Fifty-six percent of participants (n = 139) indicated that they were unemployed and 51.2% (n = 128) achieved high school or equivalent education. Most participants reported their relationship status as single or never married (72.4%, n = 181).
Table 1. Sociodemographics by treatment group of those who ranked their likelihood to vaccinate while pregnant
We do acknowledge that there is a significant difference observed in women's relationship status among the gain-frame, loss-frame, and control group. Fewer married participants or participants with domestic partners were in loss-frame group. We also note that 8 participants who were divorced or separated were also from the loss-frame group.
Main study findings
Among women who believed that the influenza vaccine was over 80 percent effective, there was a 10-fold increase in intention to obtain an influenza vaccine during their pregnancy compared with those who believed the vaccine to be less effective against influenza [OR = 10.53, 90% CI: (4.34, 25.50)] (). For example, a woman who believed the vaccine was highly effective had a 30% to 60% increase in likelihood of later obtaining it. Respondents were more likely to indicate intent to immunize if they perceived higher susceptibility of becoming ill with influenza during pregnancy [OR = 3.83, 90% CI: (1.75, 8.36)]. Women with normative support surrounding immunizations expressed greater intent to obtain the seasonal influenza vaccine than those who did not [OR = 3.27, 90% CI: (1.48, 7.26)]. There was a 2.3-fold increase in intention to immunize during pregnancy among women who had been immunized against influenza within the past five y compared with those who had not obtained influenza immunization in the past 5 y [OR = 2.31, 90% CI: (1.06, 5.00)].
Table 2. Factors associated with the likelihood of obtaining influenza immunization during pregnancy
Because the majority of respondents in the study were minority (Black/African American and Hispanic/Latina) women, race and ethnicity were not a significant factor affecting intent to immunize during pregnancy. In addition to controlling for all of the variables tested, the final multivariate model for this outcome also controlled for variables such as perceived severity of flu during pregnancy, perceived or anticipated side effects associated with influenza immunization, myths and misperceptions such as potential to get influenza from flu shots, and perceived potential for household transmission. These additional variables were not significant in the analyses and were therefore not detailed in the table although they were included in the final model to control for confounding.
Message framing outcomes
The results of the logistic regression models between paired groups (model 1: gain v. loss, model 2: gain v. control, model 3: loss v. control) are described in . The most robust predictor of intention to obtain influenza immunization during pregnancy is seen among women who believe that the vaccine is over 80 percent effective against influenza virus [Model 1: OR = 14.66, 95% CI: (4.50, 47.78); Model 2: OR = 10.64, 95% CI: (3.78, 29.94)]; Model 3: [OR = 7.43, 95% CI: (2.45, 22.55)].
Table 3. Factors associated with the likelihood of obtaining influenza immunization during pregnancy by message type
Mothers who obtained influenza vaccines in the past five years indicated a stronger likelihood to obtain immunization during pregnancy than those who did not obtain any flu shots in the past five years [model 1: OR = 3.00, 95% CI: (1.17, 7.73)]. Mothers who believed that it is likely they will get influenza while pregnant were more likely to indicate intention to obtain the vaccine during their pregnancy as demonstrated in model 1 [OR = 3.72, 95% CI: (1.45, 9.59)], model 2 [OR = 3.21, 95% CI: (1.23, 8.35)], and model 3 [OR = 5.38, 95% CI: (1.90, 15.29)]. Additionally, mothers with normative support for immunization indicated a stronger likelihood to immunize themselves during pregnancy as shown in model 1 [OR = 2.87, 95% CI: (1.10, 7.53)], model 2 [OR = 2.98, 95% CI: (1.12, 7.93)], and model 3 [OR = 4.22, 95% CI: (1.48, 12.01)].
Discussion
These findings demonstrate that history of seasonal influenza immunization is predictive of intention to vaccinate during pregnancy among this population of pregnant minority women. Elsewhere we have indicated that influenza immunization during pregnancy has a strong effect on women's subsequent intention to immunize infants.Citation32 Accordingly, we can expect that women with immunization experience are likely to be immunized in the future, including during pregnancy. In order to improve immunization rates among this population, vaccine messages must target women who have not received the seasonal influenza vaccine, encouraging these women to enter a regular pattern of influenza immunization.
As expected, single message exposure was not a significant factor in determining women's intent to immunize during pregnancy. These results provide further compelling evidence that effective health communication must occur regularly and repeatedlyCitation30,31 in order to encourage a target population to engage in the proposed behavior. Prior advertising research suggests that an individual may need to see an advertisement or message multiple times, think about it, discuss it with friends, family and/or community members and then be persuaded to adopt the proposed behavior or product.Citation30 As a result, single exposure to a message, whether gain- or loss-framed, is unlikely to change individual intention and decision-making behavior within a target population.Citation33
Women who thought the vaccine was 80% effective or greater (the highest OR) were far more likely to obtain immunization while pregnant compared with those who thought that the vaccine was 70% effective or less. While it is unsurprising that a perception of higher efficacy is more persuasive in obtaining immunization, seasonal influenza vaccine efficacy is less than 80% for pregnant women,Citation34 and the perception of high efficacy is unrealistic. This suggests that if vaccine efficacy increases, more pregnant women would be encouraged to obtain immunization. In addition, the evidence suggests that increased, repeated communication about the benefits of immunization offers the best chance to persuade pregnant women to obtain immunization.
Although age was not found to be a significant confounding factor among this population, the large proportion of those in the younger age range (18–25 y) in our cohort may have influenced their view of presented health messages. This is especially important in view of their overall vulnerability to influenza infection and associate severity of disease.Citation35,36 Prior studies have indicated challenges with processing gain- and loss-framed messages in light of lower perceived risk among younger women and adolescents.Citation37-39 Thus, compared with the older counterparts, a body of literature points to the fact that younger persons tend to be more willing to engage in risk-taking behaviors that may translate into “collective ambivalence”Citation38 toward preventive behavior. Consequently, this attitude toward risk may result in a decision to forego immunization until a higher (≥50%) illness susceptibility threshold is crossed.Citation38,40 Therefore, the relatively young age of women in our population and perception of immunization effectiveness in the face of perceived illness risk may have altered their view of our messages.Citation41
Both gain- and loss-frame messages focused on pregnant women's perceived susceptibility to influenza virus, but lacked other critical indicators of intention to immunize during pregnancy. Our findings indicate that perceptions of vaccine efficacy and presence of normative support, in addition to perceived susceptibility to influenza during pregnancy, were significant factors in determining intent to immunize during pregnancy. Based on our findings and existing risk communication literature,Citation30,31 we suggest that vaccine education materials be presented to pregnant and expecting minority women multiple times at regular intervals. These messages should incorporate important determinants of pregnant minority women's vaccine decision-making behavior, such as effects associated with influenza illness during pregnancy and vaccine efficacy, as well as promotion of immunization as a women's health preventive norm.Citation42-44
Results from this study suggest that immunization materials need to target partners, non-pregnant family, friends, or community members. Similar studies have demonstrated their critical role on achieving healthy pregnancy outcomes related to behavioral change such as tobacco use elimination and breastfeeding practice.Citation45,46 Social support from these individuals and groups can be linked to influenza immunization that may avert preterm and low birth weight outcomes.Citation47-49 Younger women in particular, and those who are primigravida, often discuss pregnancy-related decisions with trusted family members and friends and rely heavily on their social support.Citation50-52 Such discussions may play a significant role in shaping women's attitude toward immunization during pregnancy.
Limitations
There are some limitations to this study. Convenience sampling of minority women from one southeastern city is not representative of other cities in the United States. We also had a larger proportion of the study cohort who are younger (18–25 y) and are not entirely representative of the actual population of pregnant Hispanic or African American women. Arguably, this factor may have influenced our cohort's overall perception of risk associated with influenza illness during pregnancy. Additionally, we acknowledge the potential for participatory bias as women who were agreeable to participating in the study may hold stronger views on immunization and health behaviors compared with those who did not participate in this study.
Conclusions
Promoting immunization intent among pregnant minority women, who are at significantly higher risk for influenza-related deaths and complications, is a critical public health issue. Our study provides compelling evidence that women who have received the seasonal influenza vaccine in the past are likely to do so again. Future immunization campaigns need to focus on altering negative or ambivalent attitudes, perceptions, and behaviors of women with little or no history of influenza immunization. Our study demonstrates the critical role of perceived susceptibility and efficacy, as well as normative approval from relatives and peers on vaccine decision-making. In order to influence women to accept influenza immunization the findings indicate a need to develop more effective vaccines. Finally, this study reflects inadequacies associated with single message exposure to motivate immunization behavior. Instead, we argue the need for repeated message exposure to emphasize influenza susceptibility and related vaccine benefits to realize greater immunization uptake among pregnant minority women.
Materials and Methods
Formative research
We conducted 20–30 min semi-structured interviews with pregnant Black/African American and Hispanic women ($20 compensation per subject) at clinics throughout Atlanta. Data were collected until saturation was achieved on emergent themes that informed the development of two intervention message types. Based on these formative interviews, the following information was presented all to women, including those in the control condition, on the first page of their questionnaire:
“Information about the Flu Shot
Although pregnant women are about 1% of the US population, they made up 5% of US deaths from 2009 H1N1 (swine flu) reported to the Centers for Disease Control (CDC) from April 14 – August 21, 2009. According to a study done during the first month of the outbreak, the rate of hospitalizations for 2009 H1N1 was four times higher in pregnant women than other groups.
Seasonal flu shots have been given safely to millions of pregnant women over many years. As in previous years, vaccine companies are making plenty of preservative-free flu vaccine as an option for pregnant women and small children. The flu shot (not the nasal spray) is safe for pregnant women during any trimester. Nursing mothers can receive a flu shot or the nasal spray. One shot will last all flu season, even if you get it early in the season.”
The resulting gain-framed message included approximately four lines of information about influenza vaccination with a background visual depiction of a pregnant woman. The loss-framed message included four lines of text emphasizing the risks of not protecting oneself and the unborn child(ren) from influenza.
Study design and sample
Cohort recruitment began at the inception of influenza season in September 2011 and concluded in May 2012. This enabled the study team to evaluate message framing under normal conditions where the women may or may not have exposure to other influenza immunization campaign messages. Eligible individuals were women aged 18–50 y who self-identified as Black/African American or Hispanic, had not already received an influenza or T-dap vaccine during the 2011–2012 influenza season, and were able to provide written informed consent. Project staff conducted sampling in a variety of consenting venues across metropolitan Atlanta.
Women who met the eligibility criteria and agreed to participate (n = 251) were randomized to one of three conditions: single exposure to gain-framed, loss-framed, or control messages. They were interviewed that day and were compensated $20 for time and inconvenience. No information was kept for ineligible participants. All participants were pregnant at the time of the interview.
Measurement
Study materials were developed in English and Spanish. Prior to administration, bilingual community members reviewed these documents to ensure item comprehension and readability. The final survey had a Flesch-Kincaid reading score of 7.4, in either language, which met the acceptable criteria of 6–8th grade reading level for our target population.Citation53,54
Assessment of intent
Intent to immunize was assessed by asking “On a scale of 0 (definitely not) to 10 (definitely so), please rank your likelihood of getting a flu shot during your pregnancy.” Subsequently, we dichotomized variable that allowed us to evaluate those “likely” (responded 6 through 10) and “not likely” (responded 0 through 5) to obtain influenza immunization during pregnancy.
Assessment of demographic and behavioral correlates
Initial survey questions assessed sociodemographic measures (e.g., age, race/ethnicity, education, healthcare utilization, employment status). Key behavioral indicators were assessed, including immunization history for illnesses other than seasonal or pandemic influenza (e.g., Hepatitis B), healthcare seeking motivation, and willingness-to-pay for the seasonal influenza vaccine (i.e., $0/free to ≥ $30) using a 5-point scale.
Given the extent of evidence suggesting the importance of normative approval in vaccine decision-making,Citation55,56 we designed a composite measure comprised of three items to assess the perceived approval of doctors, work colleagues, family, and friends in deciding to obtain influenza immunization during pregnancy. The scale included the following items: “I think my doctor would approve of me getting the flu shot while pregnant,“ “I think people I work with would be supportive of me getting a flu shot while pregnant,” and “My friends and family would support my decision to get a flu shot while pregnant.” Each scale item was measured by a 5-point Likert scale (1-strongly disagree agree to 5-strongly disagree), designed to assign meaningful values to an underlying continuum of ratings. A team of clinicians and behavioral researchers reviewed the instrument for adequacy of the measures prior to its use. The resulting scale demonstrated strong internal consistency (Cronbach's α = 0.771) and therefore functioned as a reliable composite measure of normative support for this study.
Assessment of vaccine efficacy perception
Because this is a community-based study the clinical term “vaccine effectiveness” is often interchangeably used with the colloquial phrase of “vaccine protectiveness.”Citation36,37 We therefore adopted this term in our survey as women perceive vaccine effectiveness as a means to protect themselves from becoming infected rather than experiencing a reduction of risk.Citation57,58 The perception of influenza vaccine efficacy was therefore assessed by asking “Please indicate how protective you think the flu vaccine will be for pregnant women,” with a an associated range of 0% (“Not Protective”) to 100% (“Completely Protective”) on the continuum scale. Subsequently, we performed a median split procedure on values women assigned to this question. The resulting dichotomized variable enabled us to evaluate the threshold at which influenza immunization was perceived as “effective” (i.e., resulting values of 80–100%) compared with the range at which it was considered to “not or less effective” (i.e., resulting values of 0–70%) among our cohort.
Statistical analyses
We conducted descriptive analyses, two sample t tests, and cross-tabulations to evaluate characteristic differences observed among enrolled arms. Multiple logistic regression analyses were performed to evaluate the association between predictor variables (i.e., psychosocial indicators of health, message framing, past immunization history) and intent to immunize, while accounting for the influence of confounding. Confounding variables were selected based on the relationship between outcome and exposure variables. If any of the related variables changed the influence of different messages on vaccine intention by at least 10%, we considered these confounders and subsequently excluded the items from the final model. We also assessed the potential for multicollinearity using a condition index of 20 and a VDP level of 0.5 when full model was determined.Citation59,60 Rigorous testing indicated that no collinearity was found in the model.Citation61
In addition, we generated three multiple logistic regression models in order to compare effects across exposure groups (i.e., gain frame vs. control, loss frame vs. control, and gain frame vs. loss frame). For each paired-group comparison, we ran a multivariate logistic regression that assessed the relationship between the study group and our primary outcome – intention to obtain seasonal influenza immunization during pregnancy. This allowed us to analyze potential variations between intervention arms in the association between predictor variables and intent to immunize during pregnancy.
Disclosure of Potential Conflicts of Interest
There were no potential conflicts of interest.
Acknowledgments
The authors would like to offer our gratitude to Drs. Robert Davis and Ruth Berkelman, and Ms. Ellen Whitney for their support and guidance throughout this study. Special thanks to all participants for their involvement in the study and to Mr. Rick Kern, MixIt Marketing, for assistance with message concepts. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the CDC.
Funding
This study was partially supported by a Kaiser Permanente Georgia community benefits grant and a grant from the Centers for Disease Control and Prevention (CDC) grant 5P01TP000300 to the Emory Preparedness and Emergency Response Research Center, Emory University.
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