Introduction

Older adults are at an increased risk of complications, hospitalizations and death due to many vaccine-preventable diseases, including, but not limited to, COVID-19, shingles, pneumonia, and influenza [1,2,3,4]. They are also more likely to be vaccinated than their younger counterparts [5,6,7]. However, even with elevated health risks and government recommendations for immunizations [8], some older adults are reluctant to get vaccinated. Moreover, vaccination rates for older adults can vary geographically. In North Dakota (ND), data from the North Dakota Department of Health and Human Services (NDDoHHS) indicate that immunization rates for many vaccines among adults aged 65 and older remain lower than those seen nationally, including for influenza (US: 69.7%, ND: 56.6%); COVID-19 (at least one dose) (US: 95%, ND: 79.7%); pneumococcal (US: 70%, ND: 59.4%); and shingles (at least one dose) (US: 45.7%, ND: 41.3%) [9,10,11,12,13,14]. Lower vaccination rates among ND older adults could be due to the rural nature of the state as research has shown more rural areas in the US have lower vaccination rates than urban areas [15, 16]. However, to improve vaccine uptake among older adults, especially those located in more rural areas, it is important to better understand the factors that deter this population from getting vaccinated as well as those that might motivate positive vaccination behaviors.

Many factors have been shown to positively influence overall vaccine uptake among older adults. Physician recommendations are impactful at increasing immunization rates among older adults [17, 18]. Healthcare providers are seen as a trusted source of vaccine information for older adults [19], and physician recommendations have consistently been associated with increased vaccine uptake for a variety of vaccines including, but not limited to, COVID-19 and influenza [20, 21]. Recommendations from family and friends have also been found to influence immunization behaviors among older adults [22, 23]. A recent study of factors influencing older adult influenza uptake [23] found family and peer input to be a vital part of vaccine decision-making for older adults as it provides an opportunity for individuals to be exposed to additional vaccine information and viewpoints, although this source of input has been associated with both high and low vaccine uptake among older adults. Increased access to accurate information, thereby increasing knowledge of vaccine-preventable diseases and the importance of vaccines, has also been associated with increased vaccination rates among older adults [24]. However, little research has focused specifically on understanding vaccine motivators of older adults located in rural contexts, or specifically among those with lower vaccination rates.

Conversely, previous research has also identified a variety of issues which can deter older adults from accepting recommended vaccines. Structural barriers, such as limited physical access to vaccines, have been identified in the literature [25] and linked to lower vaccination rates. Such barriers include a lack of access to primary care, such as limited clinics or pharmacies at which to obtain a vaccination, which can be more prevalent in rural areas [26, 27]. Cost has also been identified as a deterrent to vaccination among older adults [28], but especially for the shingles vaccine [17]. Individual perceptions related to disease susceptibility and health beliefs have also been recognized as deterrents to being immunized for older adults. Specifically, a myriad of research has identified having a low perceived susceptibility to specific diseases (e.g., perceiving good health) as a rationale for many older adults to not get vaccinated [29,30,31,32]. A fear of adverse and unintended side effects of the vaccine itself has also been shown to be a major barrier to getting vaccinated among older adults [33,34,35].

A lack of information (1) related to the importance of getting vaccinated [33], (2) on the safety and efficacy of vaccines [34], and (3) from physicians about recommended vaccines [36], have been shown to contribute to a reduction in vaccine uptake among older adults. Additionally, while not a new issue, since the development and dissemination of COVID-19 vaccines, trust and confidence issues have become major deterrents to vaccination among older adults. For instance, both a lack of trust in the COVID-19 vaccine development process due to the relatively quick development of both the primary series and subsequent boosters [37] and limited trust and confidence in healthcare and government agencies recommending COVID-19 vaccines to older adults [38], have been deterrents recently.

Despite this burgeoning research on immunization motivators and deterrents for older adults, there is a relative lack of research focused on older adults in more rural geographic areas, such as ND. The aim of this study was to identify motivators and deterrents which may influence vaccine decisions among undervaccinated older adults in North Dakota. Better understanding these issues for older adults, specifically North Dakota older adults, may assist public health professionals to address these concerns among populations in rural states, through the design of tailored interventions, thereby increasing vaccination uptake and improving health outcomes for this population.

Methods

A mail survey was conducted with community-residing older adults in North Dakota (ND) aged 65 and older from May to June 2022. As part of this larger, cross-sectional study, one of the goals of the survey was to determine vaccine deterrents and potential vaccine motivators among those older adults considered under-vaccinated. This research was approved by the North Dakota State University Institutional Review Board and informed consent was obtained from participants prior to completing the survey.

Sample

Study inclusion criteria included being 65 years of age or older, living in ND, being community-dwelling, and English-speaking. Using primary COVID-19 vaccine completion as a surrogate for vaccine status, counties in ND were categorized and identified as either a “high vaccine county”, with at least a 75% completion rate (73.6% of ND counties were categorized as a “high vaccine county”), or a “low vaccine county”, with less than a 75% completion rate (26.4% of ND counties were categorized as a “low vaccine county”). A sample of 4000 adults aged 65 and older were randomly selected to receive the mail survey, with equal proportions representing high- and low-vaccination designated counties. Participant addresses were used to determine county of participants. Rural respondents were oversampled [39]. An overall survey response rate of 23.4% was attained based on the 901 completed and returned surveys, following adjustments for surveys mailed to inaccurate addresses and individuals who had died.

Measures

Vaccination Status. Respondents were asked to indicate their vaccination status for five different vaccines: influenza (number received in the last 5 years), pneumococcal (yes/no), shingles (yes/no), and COVID-19 (number received 0–4). An overall vaccine score was calculated for each individual by summing the total vaccinations received. The potential total vaccine score was 11 if an individual received all of the potential vaccines. Respondents were considered to be undervaccinated if they received less than half of the potential vaccines (5 or fewer), and were considered to be mostly/fully vaccinated if they received at least half of the potential vaccines (6 or more).

Vaccination Motivators. All respondents, regardless of vaccination status, were asked to indicate what would make it more likely they would get any vaccine from a list of potential vaccine motivators, including: more information; doctor/healthcare provider recommendation; friends/family recommendation; easy access to the vaccine; vaccine given as a nasal spray; and having the vaccine provided at no cost. Respondents were also given the opportunity to provide any additional motivators for receiving a vaccine (as an open-ended response).

Vaccination Deterrents. For each vaccine type, respondents who indicated they had not received the vaccine at least one time (for influenza in the past 5 years) were asked to specify why. Participants indicated potential deterrents by vaccine-type from a list that included: concerned about side effects; vaccines are dangerous; I’m healthy and do not need it; I don’t have enough information; and I don’t like to get shots. Respondents were also given the opportunity to provide any additional deterrents for not receiving a vaccine (as an open-ended response).

Data Analysis

SPSS 29 was used for data analysis (IBM Corp, Aramonk NY). Chi square tests were used to assess differences in vaccination status by demographic characteristics as well as by vaccine uptake. Chi square tests were also used to assess differences in vaccine motivators by vaccination status. Differences in vaccine deterrents for undervaccinated individuals were examined for each vaccine.

Results

Descriptive Statistics

Most respondents (82.1%) were mostly/fully vaccinated, whereas 17.1% were undervaccinated or unvaccinated. As shown in Table 1, there were significant differences between vaccination status groups by age (Undervaccinated: 73.1; Mostly/fully vaccinated: 74.9, p = 0.01) and rurality (Undervaccinated: 81.7%; Mostly/fully vaccinated: 69.3%, p = 0.004). There were no significant differences between vaccine status groups by gender (Female: Undervaccinated—54.2%; Mostly/fully vaccinated—53.5%), marital status (Married: Undervaccinated—64.4%; Mostly/fully vaccinated—68.7%), or education (Some college or more: Undervaccinated—69.9%; Mostly/fully vaccinated—77.2%). Undervaccinated respondents were significantly less likely than mostly/fully vaccinated respondents to receive any of the specified vaccines (For all vaccines [COVID-19, pneumococcal, shingles, influenza]: p < 0.001). Undervaccinated respondents were most likely to indicate they had received at least one COVID-19 vaccine (57.6%), followed by the shingles vaccine (35.6%), receiving the influenza vaccine at least once in the past 5 years (34.8%), and the pneumococcal vaccine (32.6%). Mostly/fully vaccinated respondents were mostly likely to indicate they had received the influenza vaccine at least once in the past 5 years (99.5%), followed by at least one of the COVID-19 vaccines (98.4%), the pneumococcal vaccine (87.0%), and the shingles vaccine (79.1%).

Table 1 Demographic characteristics and vaccination status
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Vaccine Motivators

Table 2 presents the prevalence of motivators by vaccination status grouping: undervaccinated and mostly/fully vaccinated. For undervaccinated individuals, more information was the most frequently indicated motivator for getting a vaccine. They were nearly twice as likely as mostly/fully vaccinated individuals to indicate that having more information about vaccines would make it more likely they would get a vaccine (43.5% vs. 23.1%, p < 0.001). Undervaccinated individuals were significantly less likely than mostly/fully vaccinated individuals to indicate that having a doctor or healthcare provider recommendation was a motivator for getting a vaccine (42.4% vs. 72.7%, p < 0.001). Undervaccinated participants were significantly less likely than mostly/fully vaccinated individuals to indicate that offering no cost vaccines would make it more likely they would get a vaccine (22% vs. 37.8%, p < 0.001). Additionally, undervaccinated individuals were significantly less likely than mostly/fully vaccinated participants to specify that easy access to vaccines would make it more likely they would get a vaccine (17.4% vs. 36.7%, p < 0.001). There were no significant differences between groups in their endorsement of having a vaccine as a nasal spray or having a friend or family recommendation as vaccine motivators.

Table 2 Vaccination motivators by vaccine status
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Additional open-ended responses are provided in Table 3. The most common response was related to addressing safety and vaccine efficacy concerns (e.g. “You would have to prove to me that vaccines are safer/effective”). The next most common response provided focused on reducing disinformation, with several respondents asking for “the truth” about vaccines. Respondents were also concerned about trust in information and sources of information (e.g. “More trust in healthcare (too controlled by government)”).

Table 3 Additional vaccination motivators
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Vaccine Deterrents

Table 4 indicates the prevalence of endorsement of vaccine deterrents for each of the four vaccines. Respondents were provided the opportunity to offer other reasons as to why they made the decision not to get the respective vaccines, if applicable, and these responses are provided in Table 5.

Table 4 Vaccination deterrents by vaccine type for undervaccinated older adults
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Table 5 Additional vaccination deterrents by vaccine type for undervaccinated older adults
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Influenza. Individuals who had received no influenza vaccines in the past 5 years (n = 93) were most likely to indicate it was because they were healthy and did not need it (49.5%). They were least likely to indicate it was because they did not have enough information (4.3%). However, approximately one-third were concerned about side effects of influenza vaccination. The most common “other” qualitative response was distrust in vaccine effectiveness.

Shingles. Individuals who had not received the shingles vaccine (n = 239) were most likely to indicate their rationale was concern about side effects (23.4%), and least likely to indicate vaccines being dangerous (2.6%). Respondents who offered other reasons as to why they have not received the shingles vaccines were most likely to state that it was due to cost.

Pneumococcal. Those who had not received the pneumococcal vaccine (n = 186) were most likely to indicate their rationale was being healthy and not needing it (37.3%), and least likely to indicate that it was due to vaccines being dangerous (3.2%). Of respondents who provided other reasons why they did not get the pneumococcal vaccine, the most common response was a lack of perceived necessity, such as not being susceptible to the disease, or having a strong immune system.

COVID-19. Finally, individuals who had not received any of the COVID-19 vaccines (n = 76) were most likely to indicate that their rationale was a concern about side effects (61.8%), and least likely to indicate that it was due to not liking shots (3.9%). The most common “other” open-ended response volunteered was distrust in vaccine effectiveness.

Conclusions

Although older adults have an increased risk of morbidity and mortality due to several vaccine-preventable diseases, some older adults remain hesitant about getting recommended vaccines. The main aim of this study was to identify overall motivators and deterrents of vaccine uptake among undervaccinated older adults in North Dakota. This paper contributes to the literature on understanding vaccination rates among older adults and provides specific context to undervaccinated older adults residing in a rural state with low overall immunization rates.

A key vaccination motivator identified for undervaccinated older adults is having more information about specific vaccines. Moreover, the most common additional factor provided for increasing the likelihood of getting vaccinated was focused on addressing safety issues and concerns about vaccine efficacy, consistent with previous studies [40], thus emphasizing the need for additional information among undervaccinated individuals. Previous research has highlighted the desire for additional information about vaccines among more vaccine hesitant populations including older adults [41], focusing on such topics as efficacy and safety [42]. However, a potential related issue is that since the beginning of the COVID-19 pandemic there has been a flood of information regarding vaccines, which has been muddled by a related increase in misinformation [38]. While our research did not specify as such, what these individuals may in fact be seeking is additional reliable and valid, and potentially more trustworthy, information about vaccines. The results of the present study indicate that the provision of accurate information regarding vaccine safety and efficacy may be key in increasing immunization rates among older adults.

Additionally, having healthcare provider recommendations was also a primary motivator for vaccine uptake among undervaccinated older adults. However, they were significantly less likely than their mostly/fully vaccinated counterparts to indicate this would influence their vaccine decisions. Research has shown that healthcare providers play a vital role in the vaccination decision-making process for older adults [19,20,21]. However, our results show that physicians and other healthcare professionals may play a more diminished role among undervaccinated individuals as compared to their mostly/fully vaccinated counterparts in regards to immunization uptake. This may indicate that undervaccinated older adults do not fully trust their healthcare providers [43]. This is an issue, as trust in healthcare providers is associated with increased vaccine uptake among older adults [44]. Additionally, undervaccinated older adults, especially those in more rural areas, have been found to engage less with the healthcare system than their urban counterparts, due in part to limited access to clinics and hospitals, and the results of this study may be an indication of this trend [26, 27, 45]. This finding has implications for public health, and highlights the need to address increasing trust in and access to healthcare providers among older adults. Additionally, future research should delve deeper into further understanding those who would be considered the most trusted messengers among undervaccinated older adults.

Other factors, such as cost and improving access to vaccines, were overall less likely to motivate undervaccinated older adults to get vaccinated. This suggests that motivators for undervaccinated older adults may extend beyond logistics and financial concerns, highlighting the complex decision-making process for this population. In regards to cost, our results are unique, as much of the previous research has found affordability to be a more widespread motivator for vaccine uptake for older adults than was indicated in our study [18, 23, 46]. ND is a mostly rural state, and the cultural and social issues associated with rurality, including conservatism, as indicated by our previous work [47], might influence vaccine behaviors to a greater extent than affordability considerations. Additionally, as compared to other influencers, improving access to vaccines was also less likely to be cited as an immunization motivator among undervaccinated older adults. However, although not listed as a primary influencer of vaccine behaviors, previous research has shown that expanding access points to vaccinations for older adults can increase immunization rates among this population [18].

The most common deterrent for not obtaining the influenza or pneumococcal vaccine cited by undervaccinated older adults was that they perceived themselves as healthy and thus do not need it. The focus on good current health status as a reason not to get vaccinated, especially for influenza and pneumococcal vaccines, is borne out in prior research [29,30,31, 48]. Perceived susceptibility to disease, defined as ones’ perceived risk of contracting a disease, has been extensively researched as a barrier to vaccine uptake, and low perceived susceptibility has been associated with lower vaccination rates among older adults (e.g. [29, 49, 50]). Several factors influence perceived susceptibility among older adults, including, but not limited to, a lack of understanding of older adults’ increased susceptibility to certain infectious diseases, such as influenza [51], lack of understanding of the seriousness of symptoms of specific infectious diseases [52], and a lack of awareness of the existence of vaccines for specific conditions, such as the pneumococcal vaccine [32]. These factors can be addressed through the provision of immunization information via trusted sources of accurate information, such as healthcare providers. Thus, the barrier of low perceived susceptibility related to specific vaccine-preventable diseases could potentially be addressed through vaccine-specific healthcare provider information and recommendation provision.

Concern about side effects was the most common deterrent cited by individuals for not receiving the shingles or COVID-19 vaccines. Previous research has found that the perceived prevalence and/or severity of vaccine side effects, especially for shingles and COVID-19 vaccines, is a common barrier for getting vaccinated, particularly among older adults [19, 35, 43]. The concern about side effects is often due to misinformation spread through social media or from peers or family members [53, 54], highlighting the importance of ensuring accurate information is being disseminated through trusted sources of information, such as healthcare providers. An additional deterrent cited by many respondents specific to the shingles vaccine was related to cost. This finding is similar to previous research focusing on barriers to shingles uptake among older adults [55], and also highlights the importance of affordability in the vaccine decision-making process. It should be noted that since this study was conducted, the Inflation Reduction Act was implemented, expanding Medicare benefits and lowering drug costs, including making recommended vaccines available at no cost for individuals with Medicare prescription drug coverage [56].

Limitations

While this research expands our understanding of vaccination behaviors among undervaccinated older adults, there are several limitations that should be considered. Due to the focus on older adults in North Dakota, these results are not generalizable to a larger population. Nevertheless, the study provides greater insight into the vaccination influencers and barriers for older adults in more rural states. Additionally, the study sample was racially homogenous, and although this lack of diversity is representative of North Dakota, it restricts interpretation of results to a more diverse population. Future research should endeavor to explore vaccine motivators and deterrents among a more racially heterogenous population. Moreover, these results relied on self-report data, for immunization status as well as motivators and deterrents, which may have influenced individuals’ responses to be more favorable, including more likely to indicate having received specific vaccines. Finally, respondents were primed to consider specific motivators and deterrents of immunizations, and this may have resulted in a lack of consideration of other factors which may positively or negatively impact vaccine uptake.

Conclusions

Our results support many established research findings in vaccine hesitancy research among older adults, namely the necessity to provide accurate information about vaccines, the need for trust-building, as well as addressing low perceived susceptibility for vaccine-preventable diseases. However, this research also highlights unique aspects, including the reduced influence of healthcare provider recommendations for undervaccinated older adults, and heightened focus on side effects. These results suggest a need for tailoring interventions for older undervaccinated adults in rural states to address these distinct vaccination motivators and deterrents and increase vaccine uptake.