Influenza Vaccination Among Adults with Cardiovascular Disease in the United States: Results from the Behavioral Risk Factor Surveillance System 2018–2019

Abstract

Influenza causes significant morbidity and mortality among adults with cardiovascular disease (CVD). In nationally representative surveys of 101,210 individuals with CVD conducted in 2018 and 2019, the self-reported rate of vaccination was only 50%, with significant disparities by race and education. We advocate that cardiologists not only routinely emphasize vaccination but capitalize on the opportunity to vaccinate patients at office visits to improve overall rates of vaccination and their associated racial disparities.

1. Background:

On the basis of the 2017 National Health Interview Survey, the age-adjusted prevalence of all types of heart disease was 10.6%.¹Although acute and chronic therapy for cardiovascular disease (CVD) have improved in recent years, individuals with prevalent CVD remain at high risk for acute, potentially fatal superimposed events. Acute infection with influenza increases both cardiovascular and all-cause mortality.^2,3 In one study of 80,261 patients hospitalized with influenza, 11.7% had an acute cardiovascular event, with the most common being acute heart failure and acute ischemic heart disease.⁴ The American College of Cardiology and American Heart Association (ACC/AHA) currently recommend annual influenza vaccination as secondary prevention for individuals with coronary and other atherosclerotic vascular disease as a Class I, level of evidence B classification.⁵

While influenza vaccination decreases serious cardiovascular events, ongoing reticence about vaccines and uneven public health infrastructure challenge widespread vaccination, even among high-risk individuals.⁶ As a result, universal vaccination is difficult to achieve, but the actual proportion of adults with prevalent CVD who receive influenza vaccination is unknown. In this study, we evaluated the prevalence of self-reported influenza vaccination among individuals living with CVD in the United States (US) using a large, nationally representative survey.⁷

2. Methods:

2.1. Data source:

We analyzed the 2018–2019 iterations of the Behavioral Risk Factor Surveillance System (BRFSS) conducted by the Centers for Disease Control and Prevention (CDC) in all 50 states, the District of Columbia, and US territories. This ongoing annual telephone survey measures behavioral risk factors in adults (≥18 years of age) in the US. A random sample of adults (one per household) are surveyed through a yearly telephone survey conducted by state health personnel or contractors, and it is considered the largest telephone survey in the world.⁷ The CDC provides post-stratification weights to enable nationally representative projections of all American adults.⁷

The questionnaire comprises a core component, administered to all individuals, and additional modules and questions that specific states select. The total sample sizes were 437,436 in 2018 and 418,268 in 2019. Response rates for BRFSS are calculated using standards set by the American Association for Public Opinion Research and defined as the number of respondents who completed the survey as a proportion of all eligible and likely-eligible individuals, whether or not they were actually contacted.⁸ The median survey response rates for all states, territories, and Washington, DC, were 49.9% in 2018 and 49.4% in 2019.⁹

The protocol for our analyses was subjected to ethics review by the Beth Israel Deaconess Medical Center Committee on Clinical Investigations (protocol 2005P-000328), which provided an exemption from continuing review.

Each year, participants separately reported the presence of CVD by answering yes or no questions to “has a doctor, nurse, or other health professional ever told you that you had angina, coronary heart disease, or a stroke?” Influenza vaccination was queried as “during the past 12 months, have you had either a flu shot or a flu vaccine that was sprayed in your nose?” Additional behavioral characteristics included in our models were sex (male vs female), age (stratified at age 65), education (advanced degrees and college/some college vs no college), census region (northeast, South, Mid-West, West), and self-report of diagnosed diabetes, asthma, chronic obstructive pulmonary disease (COPD), and chronic kidney disease (CKD). Race was subdivided into White, Black, Hispanic, and other (including multiracial, Asian, and not reported).

2.2. Statistical analysis:

We performed cross-sectional analyses using STATA/IC 16.1 (StataCorp, College Station, TX, 2020). We included all respondents who reported a clinician diagnosis of angina, coronary heart disease, or stroke (n=101,210). We used survey-weighted logistic regression to determine disparities in vaccination status by demographics, including sex, age, education, race, region, and chronic health conditions.

2.3. Sources of funding:

This work was supported by the National Institute on Aging (K24AG065525).

3. Results:

A total of 101,210 individuals, corresponding to approximately 21 million Americans, reported having CVD in the form of angina, coronary heart disease, or stroke. In this population, only 50.4% (95% CI: 49.7–51.1) received an influenza vaccine within the past year.

In mutually adjusted analyses, we observed no difference by sex (OR for men vs women 0.98, 95% CI: 0.91–1.03, p=0.65). Adults ≥65 years of age were more like to report vaccination than those <65 (OR 2.29, 95% CI: 2.15–2.42, p<0.01). Those with some college education were more likely to report vaccination than those without college education (OR 1.19, 95% CI: 1.13–1.27, p<0.01). Compared to White respondents, Black (OR 0.81, 95% CI: 0.75–0.88, p<0.01) and Hispanic (OR 0.83, 95% CI: 0.72–0.96, p=0.01) individuals were less likely to report vaccination. College education largely equalized rates between White and Other respondents but did not do so for Black and Hispanic adults (Figure 1). Furthermore, as seen in Figure 1, the proportion of people with CVD who reported vaccination generally increased with some college education, although this was discrepant for the Hispanic subgroup. We observed no significant variation across geographic regions of the US (p=0.46). Respondents with diabetes (OR 1.32, 95% CI: 1.24–1.41, p<0.01), asthma (OR 1.12, 95% CI: 1.05–1.22, p<0.01), CKD (OR 1.37, 95% CI: 1.24–1.51, p<0.01), and COPD (OR 1.16, 95% CI: 1.08–1.25, p<0.01) in addition to CVD were also more likely to report recent vaccination.

Figure 1:

National population proportions of adults with CVD who reported receiving an influenza vaccination by race and education

4. Discussion:

Despite recommendations for universal influenza vaccination for patients with CVD by the ACC/AHA and Centers for Disease Control and Prevention, influenza vaccination among individuals with clinician diagnosed CVD in the US is poor, with only half of this population reporting up-to-date vaccination in 2018–2019.^5,10 Ensuring vaccination status is of rising importance, as recent data suggest that vaccination is associated with a lower risk of acute heart failure and acute ischemic heart disease in conjunction with influenza (RR 0.86 and 0.80, respectively), potentially indicating that influenza vaccination has a cardioprotective effect aside from just influenza prevention.^4,11,12 This cardioprotective effective is being actively studied in randomized trials (RCT-IVVE: NCT 02762851, IAMI: NCT 02831608).^13,14 Additionally, the secondary cardiovascular prevention effectiveness of influenza vaccination has been shown to be comparable to smoking cessation, antihypertensives, and statins, further supporting its routine necessity.¹⁵

We observed clear racial disparities in vaccination status; Black and Hispanic individuals with CVD are less likely to be vaccinated than were White individuals with CVD. Additionally, even with similar education levels, White individuals still have a greater proportion of vaccination than Black and Hispanic individuals. Unexpectedly, the higher levels of vaccination associated with greater education were not observed among Hispanic respondents. This may be due to the smaller sample size in this specific subgroup.

Overall, racial disparities are well-documented in vaccination, and our results suggest that they persist even among individuals at highest influenza risk (and even after adjustment for geography and concurrent conditions).^16,17 The CDC developed the Racial and Ethnic Adult Disparities in Immunization Initiative (READII) in 2002 for this reason.¹⁸ Unfortunately, years later, as evident by our results, public health infrastructure continues to struggle with this disparity. Ongoing research is paramount in understanding the historical, socioeconomic, and cultural complexities for vaccination inequality and correcting it, particularly given the superimposed burden of COVID-19.

To improve influenza vaccination prevalence and help mitigate racial disparities, we advocate that cardiologists not only routinely emphasize vaccination, but capitalize on the opportunity to vaccinate patients at office visits. In a national random sample, Davis et al. showed that only 54% of cardiology practices had influenza vaccination available, whereas endocrinology was 78% and pulmonology 90%.¹⁹ Cardiologists often see patients multiple times a year; as such, a promising opportunity exists to increase access to vaccination for these patients.

Limitations of this study include its self-report of both influenza vaccination, cardiovascular disease status, and comorbidities, so population estimates may be somewhat misclassified, although BRFSS estimates are widely used for policymaking and resource allocation.⁷ In addition, we had limited ability to conduct subgroup analysis due to smaller sample sizes, which hinders firm conclusions about the joint effects of race and education. Furthermore, no information is collected on the severity of CVD nor on visits to specialists, limiting our ability to determine if cardiology access might increase or decrease vaccination rates. At the same time, strengths of our study include its up-to-date nature, with very recent estimates of vaccination, large sample size, geographic diversity, and nationally representative nature. It is unlikely that any other survey could provide more recent estimates in as large, diverse, and representative a sample.

5. Conclusion:

Only 50% of the US population with CVD reported up-to-date influenza vaccination despite its proven benefit in this population. Rates are particularly low among underserved minorities. To improve this gap, cardiologists should consider incorporating influenza vaccination into routine cardiovascular care.

Table 1:

Odds ratios of influenza vaccination in individuals with CVD by demographics

	Unadjusted Odds Ratio (95% CI)	Adjusted Odds Ratio (95% CI)
Male Sex	0.99 (0.93–1.05)	0.97 (0.92–1.03)
Age ≥65 years	2.39 (2.26–2.54)	2.29 (2.15–2.42)
College Education	1.23 (1.16–1.29)	1.19 (1.13–1.27)
Race
White	reference	reference
Black	0.71 (0.66–0.77)	0.81 (0.75–0.88)
Hispanic	0.62 (0.55–0.71)	0.83 (0.72–0.96)
Other	0.88 (0.74–1.05)	1.01 (0.83–1.22)
Medical History
Diabetes	1.42 (1.33–1.51)	1.32 (1.24–1.41)
Asthma	1.05 (0.98–1.12)	1.12 (1.05–1.22)
CKD	1.54 (1.40–1.68)	1.37 (1.24–1.51)
COPD	1.26 (1.18–1.34)	1.16 (1.09–1.25)

^*“*Variables adjusted for were sex (male vs female), age (stratified at age 65), education (at least some college vs no college), race (White, Black, Hispanic, and other - including multiracial, Asian, and not reported), self-report of diagnosed diabetes, asthma, chronic kidney disease (CKD), chronic obstructive pulmonary disease (COPD), and census region (Northeast, South, Mid-West, West

Table 2:

National population proportions of adults with CVD who reported receiving an influenza vaccination by demographics

Sex
Male	0.51
Female	0.50
Age
≥65 years	0.61
<65 years	0.39
Education
≥ college	0.52
< college	0.48
Race
White	0.53
Black	0.45
Hispanic	0.42
Other	0.50
Medical History
Diabetes	0.56 (no diabetes 0.48)
Asthma	0.51 (no asthma 0.50)
CKD	0.60 (no CKD 0.49)
COPD	0.55 (no COPD 0.49)