US seniors' intention to vaccinate against RSV in fall and winter 2023–2024

Abstract In the fall and winter of 2023–2024, the United States may experience a “tripledemic” of COVID-19, influenza, and respiratory syncytial virus (RSV) that may lead to 100 000 deaths. Seniors will be disproportionally affected. The newly released RSV vaccines for those age 60 years and over may reduce the number of deaths for the expected 6000 to 10 000 seniors expected to die from RSV alone. Using a large national survey, we queried Americans over age 60 about their RSV vaccination status and their intention to vaccinate this fall and winter. We found that 9% of seniors had already been vaccinated. Of the remaining unvaccinated, 42% indicated their intent to vaccinate. We found that those with higher levels of concerns for the disease, higher levels of self-assessed risk, believing that vaccines were safe and important, higher levels of trust in health institutions, and men were more likely to seek out vaccinations. Vaccine-hesitant respondents listed a lack of necessity, concerns about side effects and safety, and a lack of information as primary reasons. The large number of unvaccinated seniors will likely lead to an excessive number of hospitalizations and deaths as well as augmented social costs. Evidence-based mitigation measures tailored to seniors' concerns should be implemented immediately.


Introduction
Respiratory syncytial virus (RSV) poses a significant health risk to populations worldwide but particularly to the very young and the old, and in those with chronic conditions. 1 Older adults above age 60 years are particularly affected.Every year between 60 000 and 160 000 US seniors are hospitalized, with 6000 to 10 000 ultimately dying of the infection. 2owever, recently, 2 vaccines became available for older adults that hold the potential to substantially reduce these numbers. 3The vaccines are 83% to 89% effective in preventing lung infections. 4,5However, there are reasons to be skeptical about how widespread vaccinations among US seniors will be in the fall and winter 2023-2024.For one, the Centers for Disease Control and Prevention (CDC) did not make an outright recommendation for the vaccines, 3 a decision that has been criticized by some. 6This ambivalence has been mirrored by various other important sources of advice for older Americans including the AARP, 7 the American Medical Association, 8 the American Hospital Association, 9 and the American Pharmacists Association. 102][23] Reducing RSV-related illness among seniors is a crucial goal because of the expected "tripledemic" of COVID-19, influenza, and RSV that may lead to 100 000 deaths in the United States this fall and winter. 24However, vaccination intentions among US seniors against RSV remain underexplored so far.

Data
To learn more about the intentions to vaccinate against RSV for Americans over 60, we fielded a nationally representative survey on September 27 and September 28, 2023, using Lucid.Lucid has been used extensively in this type of research because it provides high-quality survey data and the data have been validated against true probability samples. 25Lucid relies on quota sampling by age, educational attainment, household income, race and ethnicity, and partisan identification.Respondents are selected into the survey via a double opt-in procedure, first joining the Lucid panel and subsequently agreeing to participate in the survey. 25Lucid was compensated $1.50 per completed response.For additional details, please refer to the Appendix Exhibits 1 through 4.
Of the 7706 respondents who opted into the survey, 7360 (96%) completed the consent form and ultimately 5035 respondents completed the survey (68%).The main source of respondent attrition were 2 attention checks utilized to ensure data quality (31%).Less than 1% of respondents failed to pass the reCAPTCHA verification.A total of 1345 respondents were aged 60 and older.Data were weighted on age, gender, race, income, and education based on the Current Population Survey.The study received approval from the institutional review boards at the appropriate institutions.

Dependent variables
All respondents over 60 were asked a number of questions related to RSV and the RSV vaccine.The 2 major outcomes of interest were whether respondents had already received the RSV vaccine or, if not, whether they intended to get vaccinated this fall and winter.Those respondents who indicated that they had no plans to get vaccinated also received a list of 12 distinct reasons for their hesitation based on previous literature. 5,17,20This list included lack of insurance coverage, lack of resources, lack of information, concerns about vaccine safety, concerns about vaccine side effects, concerns about vaccine effectiveness, whether they thought vaccines were not important, whether they saw no need for the vaccine, whether the process was too complicated, whether they lacked time, whether they already had the disease, and whether it was against their religious beliefs.See Appendix Exhibit 3 and 4 for detailed wording.

Independent variables
Respondents were also asked various questions commonly asked in assessments of vaccination intentions.These questions included their self-assessed level of concern about RSV using a 5-point scale from "Not at all" to "A great deal." 17We also asked respondents to self-assess their personal risk of getting RSV in comparison to others on a 5-point scale from "much higher" to "much lower." 26We expect that those with higher levels of self-assessed concerns and those with higher levels of self-assessed personal risk will be more likely to seek out vaccinations.We also queried respondents whether they had experienced RSV previously.We expect that previous infections will positively predict intentions to vaccinate. 26We also included standard measures asking respondents whether they thought that vaccines were safe, effective, and important (all 4-point scales) with the expectation that respondents scoring higher on these measures will be more likely to seek out vaccinations. 17,27ue to the increasing politicization and polarization of vaccinations, we also included measures to assess whether respondents had voted for President Trump in 2020 and whether they considered themselves to be liberal (combining both "extreme liberals" and "liberals") or conservative (combining both "extreme conservatives" and "conservatives").We expect that Trump voters and conservatives will be less likely to seek out vaccinations, with the opposite effect for liberals.We note that we re-estimated all models replacing ideology with partisanship with analogous results (see Appendix Exhibit 7).We also expect that respondents who are more religiously active (5-point scale) will be more hesitant to get vaccinated. 28Trust in health institutions has also been shown to be an important correlate of vaccine hesitancy. 17We measured trust as a 13-point index combining standard individual trust measures for the CDC, the National Institutes of Health, the Food and Drug Administration, and medical doctors (all 4-point scales from "no confidence at all" to "a great deal"; Cronbach's alpha: .86).Additional control variables accounted for respondents' race and ethnicity, gender, age, income, education, and insurance status (Medicare, Medicaid, individual market, employer-sponsored insurance, uninsured). 17,27thodological approach First, we derived unadjusted estimates for seniors who either were already vaccinated or expressed their intent to get vaccinated.Second, we relied on multivariate logit regression utilizing survey weights to assess previous vaccination as well as intention to vaccinate against RSV because our outcome variables described above are dichotomous.Due to a lack of interpretability of logit coefficients, we then make use of average marginal effects (AMEs) to assess substantive and statistical significance of the various variables of interest. 29,30We also present odds ratios.Across these analyses, we considered a P value lower than .05as statistically significant.Third, we also we derived unadjusted estimates for the various underlying reasons that seniors provided for not seeking out vaccinations.

Results
Overall (Figure 1), 9.1% (95% CI, 7.3%-11.2%) of respondents indicated that they had already been vaccinated against RSV.Moreover, out of those who had not been vaccinated,

Correlates of vaccination and intentions to vaccinate
The logit models presented in Table 1 further parse out the correlates of previous vaccination as well as intention to vaccinate (see also Appendix Exhibits 6 and 8).Included in Table 1 are also AMEs where their P value did not exceed .05 as well as odds ratios.Assessing the group of respondents who had already received the RSV vaccine, we found that women were less likely to already have received the vaccine (AME: −0.046; P = .014).In addition, we found that those obtaining coverage in the individual market were less likely to be Health Affairs Scholar, 2024, 2(2), 1-5 vaccinated (−0.093;P < .001).Focusing on the respondents who had not yet received the vaccine, we found various correlates of intention to vaccinate.As expected, those with higher levels of concern for the disease (0.098; P < .001)and those with higher self-assessed risks for the disease (0.092; P < .001)were more likely to signal their intent to get vaccinated.The same held for those with the belief that vaccines were safe (0.105; P = .003)and important (0.094; P = .013),and those with higher levels of trust in health institutions (0.021; P = .001).We note that we did not find any statistically significant results for the political variables included.This remained the case when we re-estimated the models replacing presidential vote choice and ideology with Democratic and Republican partisanship (see Appendix Exhibit 7).However, while the statistically significant findings from our primary models remained in the re-estimated versions, we also found that those with higher levels of religious activity (−0.020;P = .045)were more hesitant to vaccinate.

Reasons provided for hesitancy to vaccinate against RSV
As noted above, we also asked respondents who had indicated that they had no intention to get vaccinated against RSV for the underlying reasons of their hesitation (Table 2).The primary drivers of hesitation included not seeing the necessity for the vaccine (25.0%;

Discussion and conclusion
Experts expect that the United States will experience a substantial number of individuals falling ill from COVID-19, influenza, and RSV this fall and winter. 24Seniors will be disproportionately affected by all 3 vaccine-preventable diseases.Our findings here indicate that only a minority of those above age 60 will seek out vaccinations against RSV, a disease that claims the lives of 6000 to 10 000 seniors every year. 2 These numbers are also much lower than comparable numbers for young children. 5Our findings indicate that intentions to vaccinate were lower among women, those who do not deem vaccines safe or important, those with lower levels of concern or self-assessed risk for RSV, and those with lower levels of trust in health institutions.As a result of the low levels of intended vaccinations, it seems likely that the United States will experience a substantial impact on its health care system dealing with a large number of individuals sick from diseases that could have been prevented or mitigated by vaccinations.Individuals who fail to get vaccinated, as well as those who medically cannot receive the vaccine, will be disproportionately affected.However, societal costs will likely be large and affect society as a whole.
Our study comes with several limitations.First, we utilized an online panel that is representative of the United States nationally along important dimensions to generate the data for our analyses.This is common practice today, and the panel we used is reputable, validated, and frequently employed for this type of work. 25We further improved data quality by using a reCAPTCHA verification procedure and 2 attention checks.Second, our data are cross-sectional in nature and thus, by definition, subject to several limitations.Third, while RSV receives media attention, it is not as well known as other vaccine-preventable diseases like influenza and COVID-19.Not all seniors may be fully aware of their risks or previous infections, for example.Last, we restricted our analyses to Americans aged 60 and older, the target group for the new RSV vaccine.As noted above, our data are nationally representative of the US adult population.However, there are no a priori reasons to assume that, accounting for our large sample, our selection would introduce potential bias into our analyses.We also utilized various survey weights to account for potential differences and found consistent results.
Given that a majority of seniors are unlikely to seek out RSV vaccinations this year, questions emerge how policymakers can respond.Policymakers ought to respond to these findings by implementing evidence-based policies that increase vaccination rates in the immediate as well as long-term future. 23Based on the findings here, these efforts should focus on highlighting the safety and importance of vaccines as well as the potential risks to individuals who fail to vaccinate. 31,32Moreover, substantial efforts are needed to counter false and misleading information about both the disease as well as the vaccines. 31,32An important role also falls to health care providers, who tend to be the most trusted source of medical advice for most individuals. 31,32oreover, given the consistent findings about increased vaccine hesitancy in women, approaches particularly tailored to women ought to be developed.Ultimately, policymakers and society would be well served if effective measures to lower vaccine hesitancy across the board were to be implemented.

Figure 1 .
Figure 1.Proportion of respondents who indicated that they are already vaccinated against RSV, are planning on getting vaccinated, and a combination of both.Weighted unadjusted estimates based on survey sample.Abbreviation: RSV, respiratory syncytial virus.

Table 1 .
Results for logit regressions for intention to vaccinate against RSV.