Investigating behaviours and attitudes regarding recommended vaccination in adults 50 years and above in Australia

Introduction

Vaccination is important to reduce the morbidity and mortality associated with infectious diseases, particularly in older adults. Unvaccinated adults can act as a reservoir of infection for vulnerable populations (Dash et al. 2019). In Australia, many vaccines are recommended under the Australian National Immunisation Program (NIP), with only some funded for specific groups. Pneumococcal vaccination is recommended and funded for Aboriginal and Torres Strait Islander adults aged ≥50 years and non-Indigenous adults aged ≥70 years, it is also recommended but not funded for younger adults with specific medical conditions (Australian Technical Advisory Group on Immunisation (ATAGI) 2022; Australian Government Department of Health and Aged Care 2023). Vaccination against herpes zoster, also known as shingles, is recommended for all Australian adults aged ≥50 years but only funded for those ≥70 years (Australian Technical Advisory Group on Immunisation (ATAGI) 2022; Australian Government Department of Health and Aged Care 2023). Annual influenza vaccination is recommended for everyone ≥6 months of age but it is only funded for specific groups including children 6 months to 5 years, people aged ≥65 years, Aboriginal and Torres Strait Islander people, and pregnant women. A single booster dose of a pertussis-containing vaccine is recommended for adults aged ≥50 years with an additional booster dose recommended at age 65 years, but is not funded (Australian Technical Advisory Group on Immunisation (ATAGI) 2022; Australian Government Department of Health and Aged Care 2023).

Adult vaccination rates in Australia are often sub-optimal, even for funded vaccines (Cheng et al. 2019; Lin et al. 2020). In 2021, influenza vaccine coverage was 23.9% in those aged 20–<50 years (Hull et al. 2022), compared to 62.1% for those aged 65–75 and 68.5% for those aged >75 years. Prior to funding under the NIP for high-risk groups and older adults, vaccine uptake was approximately 35% for adults aged 18–64 years with chronic conditions (Gonzalez-Chica et al. 2024). Pneumococcal vaccination uptake among adults was also low prior to inclusion in the NIP at under 10% for those in high-risk groups (Khandaker et al. 2024). Pneumococcal vaccine coverage for the same year was much lower, at 17.2% in those aged 70 years and 20.1% for those aged 71–79 years. Herpes zoster vaccine coverage was reported at 30.6% for those aged 70 years and 46.7% for those aged 71–79 years (Hull et al. 2022). Herpes zoster vaccine coverage pre-NIP funding was estimated at just under 20% (Bennett et al. 2023). Pertussis vaccine uptake data is limited but likely under-reported, with less than 1% coverage in adults over 18 in 2017 (Hull et al. 2019). In 2009, only 11.3% of adults reported receiving a pertussis dose (Australian Institute of Health and Welfare 2011). Research suggests that funding is a key factor in higher vaccine uptake (Dyda et al. 2016; Briggs et al. 2019).

Many factors influence adult vaccine uptake, which often differ from those affecting childhood vaccination (Eiden et al. 2022). Provider recommendation is linked to higher uptake, while lack of awareness significantly decreases it (Dyda et al. 2016; Briggs et al. 2019; Eiden et al. 2022). Other factors associated with increased uptake include positive perceptions of vaccination, poor self-reported health, and belief in vaccine effectiveness (Dyda et al. 2016). For older adults, workplace vaccination availability and perceptions of age are also key (Briggs et al. 2019). An Australian study found healthcare workers and doctors generally aware of recommendations, though patient refusal and competing priorities were common barriers (Ridda et al. 2008).

To date, there has been limited research on how to improve uptake of non-funded vaccines among adults. Canada has implemented some strategies to improve uptake of these types of vaccines, including improving awareness and changing public perception to recommended but unfunded vaccines (Scheifele et al. 2014). To increase adult vaccine uptake in Australia, more information is needed in relation to factors that impact both patients and healthcare workers. To better understand adult vaccine uptake in Australia, this study explores the factors that influence vaccination decisions among both patients and healthcare workers. Identifying these factors can inform future interventions aimed at improving vaccine coverage, particularly for unfunded vaccines. This study specifically investigates the factors affecting the uptake of recommended vaccines in adults aged ≥50 years in Australia.

Methods

Results

A total of 1012 individuals aged 50 years and above completed the survey, with 196 telephone surveys and 816 online surveys. The mean age of participants was 66.4 years (range 50–94 years). Approximately half of the participants were male (47.8%) with the remaining participants reporting their gender as female, non-binary, or transgender. The majority of participants were residents of New South Wales and Victoria (Table 1).

Discussion

Using data from a nationally representative sample, we investigated attitudes, knowledge, and uptake of recommended adult vaccines in Australia. The majority of adults reported they were vaccine accepting and had high levels of knowledge regarding which vaccines are recommended for their age group. However, only 15–23% of participants were aware that influenza, pertussis, herpes zoster, and pneumococcal vaccines were recommended for those aged ≥50 years. This is despite the fact that each vaccine is currently recommended for some portion of this age group. Findings also suggest that healthcare workers were recommending and offering vaccination, but vaccine uptake and factors associated with uptake differed by vaccine type, with lowest uptake reported for pneumococcal and pertussis vaccines. The importance of disease impacts and protection from vaccination in adults needs to be better communicated, with more than half of respondents reporting that vaccination is more important for children than adults. Additionally, the primary reason reported for not receiving a vaccine was, ‘I do not believe it is necessary’. Factors associated with vaccination differed slightly by vaccine type but being aged ≥66 years, having been offered or recommended the vaccine, and willingness to pay for the vaccine were significantly associated with uptake of all four recommended vaccines, and being female was associated with three vaccine types.

While it is encouraging that the majority of respondents were vaccine accepting, knowledge of recommended vaccines could be improved in the Australian adult population. The highest gap was in relation to pertussis with 40% of respondents reporting that they thought this vaccine was not recommended for those aged ≥50 years, despite the fact that a single booster dose of a pertussis-containing vaccine is recommended for those aged >65 years (Australian Technical Advisory Group on Immunisation (ATAGI) 2022). This reflects previous Australian data which showed a lack of awareness in relation to adult pertussis vaccination ranging from 26 to 40% (Clarke et al. 2015; Bayliss et al. 2021). Knowledge of the herpes zoster vaccine was also low, likely because this is the newest addition to the vaccine recommendations, with 2020 data showing that approximately 10% of general practitioners are not aware of the recommendations (Dey et al. 2022).

Factors associated with uptake other than knowledge of vaccination are important. Most participants were aware of the recommendation of influenza vaccine, however, only 28% of participants reported they would be vaccinated for influenza if health provider recommended. This is lower than the acceptance rate for other vaccines in the study, suggesting that for some adults in Australia knowing about the vaccine will not improve uptake.

Findings from our survey also suggest that healthcare workers were often recommending and offering vaccination. This may be improving over time; a 2014–2018 study in South Australia found that only 8% of people had been recommended a pertussis vaccine from their healthcare worker (Clarke et al. 2015) compared to 61.6% in the current study. The most commonly recommended and received vaccine in this study was influenza, which has been reported at higher rates for both in other Australian studies (Trent et al. 2021) and highlights the success of the national influenza campaign. Recommendation from a healthcare provider has been shown to improve vaccine uptake (Dyda et al. 2016), yet our results suggest that recommendation alone may not be sufficient. In this study the uptake of the other three vaccines was lower than expected, even when recommended, which suggests that other factors may influence vaccine decisions (Dyda et al. 2016).

The risk of illness may also be an important contributor. The primary reason for not receiving a vaccine if recommended was ‘do not believe it is necessary’. This was further supported by the finding that participants reported the greatest concern about the impact of herpes zoster on health, which was also the vaccine for which the highest proportion of participants were willing to pay. The perception of risk and the impact of the disease have also previously been identified as being positively associated with vaccine uptake in adults (Wheelock et al. 2014; Yeung et al. 2016). This suggests that increasing adult vaccination using education and recommendations needs to include a component that helps individuals understand that they need to be concerned about the specific disease.

The study confirmed previous findings that adult vaccine uptake is associated with willingness to pay for the vaccine (Lu et al. 2017; Kolobova et al. 2022). A systematic review on willingness to vaccinate against herpes zoster found one of the main reasons for vaccine unwillingness was financial concern (Wang et al. 2023). As stated, participants in our study reported the highest willingness to pay for the herpes zoster vaccine, likely due to the perception of significant impact on health, yet rates of uptake in this sample remain sub-optimal. Studies focusing on COVID-19 vaccine uptake found willingness to pay was highly sensitive to pricing, with level of support decreasing with price increases (Wong et al. 2024). Removing out-of-pocket costs has been seen to influence vaccine uptake in several countries. In the United States, adult herpes zoster virus vaccination rates significantly increased once private insurers covered vaccination costs (Churchill and Henkhaus 2022), and following the introduction of universal funding, coverage of pneumococcal and influenza vaccine were seen to increase among Australian adults (Dyda et al. 2016).

Being aged ≥66 years and being female were the most common factors associated with vaccine uptake. The increasing likelihood of vaccination uptake in older individuals is consistently reported across the literature and likely reflects both funding and perceived risk (Dyda et al. 2016). The association between adult vaccination uptake in Australia and being female has also previously been reported in the literature, although not as consistently (Dyda et al. 2016). This reflects previous findings in relation to men’s healthcare seeking behaviours in general. Studies have identified that men have shorter consultations with general practitioners and are more likely to seek help at later stages of illness (Holden et al. 2006; Martin et al. 2007). Women also commonly attend primary health care more often than men (Australian Bureau of Statistics 2021–2022).

There are several limitations to consider in the interpretation of these results. There were wide confidence intervals for certain categories, particularly where high response proportions led to larger estimates. However, the overall trends remain, with the confidence intervals providing important information on the distribution of responses across different subgroups.

Data were self-reported, which is inherently limited by recall bias. However, previous investigation into the reliability of self-reported vaccination data shows that people accurately recall having an influenza vaccine over 95% of the time. This is slightly lower for influenza vaccines given more than a year ago and pneumococcal vaccines (King et al. 2018; Smith et al. 2021). Neutral responses were classified as vaccine hesitant to reflect uncertainty and maintain consistency, however, there may be other factors related to ‘Neither agree nor disagree’ which are not related to vaccine hesitancy. Additionally, more nuanced questions regarding knowledge in adults by specific vaccine type may be of benefit. In this study, participants were asked about recommendations for each of the included vaccines in those aged ≥50 years, but recommendations vary by age and specific sub-population, making it difficult to assess knowledge about details.

Conclusion

Two key factors most likely to impact vaccine uptake in adults were identified: the risks associated with non-vaccination, and recommendation from a healthcare professional. Firstly, the importance of vaccination and risks associated with lack of vaccination need to be highlighted to this population. Secondly, recommendations from healthcare professionals continue to be one of the most important facilitators for uptake, hence strategies to improve health risk communication may be beneficial. Overall, adults reported they are unlikely to pay for recommended vaccines, making increasing uptake of these vaccines difficult.