Flu Vaccination and Older Hospitalized Adults with Cardiovascular Disease: What are the Benefits?

Yuangmu Huang, MD, assistant professor and associate researcher at the school of public health at Peking University in Beijing, China, and colleagues conducted the study.

According to the study authors, globally influenza causes between 291,000–646,000 deaths per year.¹ Older adults are at higher risk, but there is scant evidence on how vaccination affects hospitalizations for adults with cardiovascular disease (CVD). Huang and colleagues said that randomized controlled trials have offered some insight showing positive effects, and observational studies have shown the possibility of collecting real-world data.^2,3,4 “These studies have enabled the evaluation of influenza vaccination on a broader range of diseases and among individuals with wider demographic characteristics,” researchers wrote.¹

Huang and colleagues extracted data from the Beijing Urban Employee Basic Medical Insurance database from January 2013 to December 2019 to examine 713,488 records of adults aged ≥60 years old with CVD who were hospitalized.¹ Adults included in the study had a primary discharge diagnosis of stroke and ischemic heart disease (IHD). Researchers used the Beijing Elderly Influenza Vaccination database to determine patient vaccination status. They used logistical regression with generalized estimating equations, adjusting for unmeasured cofounders, to see if influenza vaccination affected the rate of repeat hospitalizations and in-hospital mortality.¹

Researchers found that only 13.3% (95,060) of older adults who had been hospitalized for CVD had gotten a flu vaccine, while 618,428 (86.7%) were unvaccinated.¹ Vaccinated patients were more likely to be female, older, have fewer inpatient visits, and have fewer comorbidities. Researchers said vaccinated patients were also less likely to have an alcohol-related diagnosis and were more likely to have had a surgical operation.

Researchers reported that during the flu seasons for this study from 2013-2019, 7822 of the study patients with CVD died.¹ There were 110,180 recurrent hospitalizations: 69,459 were CVD related and 7909 were for respiratory diseases.¹ “During the summer months, 3555 patients with CVD died, and 23,843 had recurrent hospitalization (14,586 for CVD, 1276 for respiratory diseases),” the authors said.¹

Huang and colleagues reported that there was a 15% reduction in the risk of in-hospital death for patients with CVD in the adjusted model (odds ratios 0.85 [0.74, 0.99]).¹ This association was stronger for ischemic stroke patients (19%, odds ratio 0.81 [0.60, 1.06]).¹ There was a 13% reduction in death for hemorrhagic stroke (odds ratio (0.87 [0.60, 1.27]).¹ Researchers noted the confidence intervals were wide due to the low number of events. “For in-hospital death, the protective association of influenza vaccination was stronger in patients with fewer comorbidities and was similar to that of joint vaccinations of influenza and pneumococcal vaccinations,” the authors noted.

Vaccination also reduced recurrent hospitalizations. The adjusted model showed a 6% (odds ratio (0.94 [0.88, 0.99]) lower risk for IHD and a 28% (odds ratio (0.72 [0.56, 0.93]) lower risk for respiratory disease in patients with IHD.¹ Huang and colleagues said there was no association in patients with stroke.

“Our findings add to the evidence base supporting the recommendation of annual influenza vaccination in older adults. Comprehensive interventions are necessary to improve the coverage of influenza vaccination among older adults hospitalized for CVD to prevent adverse hospitalization outcomes,” researchers concluded.

References

1. Pang Y, Liu X, Liu G, et al. Effectiveness of influenza vaccination on in-hospital death and recurrent hospitalization in older adults with cardiovascular diseases [published online ahead of print, 2022 May 30]. Int J Infect Dis. 2022;122:162-168. doi:10.1016/j.ijid.2022.05.059
2. Demicheli V, Jefferson T, Di Pietrantonj C, et al. Vaccines for preventing influenza in the elderly. Cochrane Database Syst Rev. 2018;2(2):CD004876. Published 2018 Feb 1. doi:10.1002/14651858.CD004876.pub4
3. Anderson ML, Dobkin C, Gorry D. The Effect of Influenza Vaccination for the Elderly on Hospitalization and Mortality: An Observational Study With a Regression Discontinuity Design. Ann Intern Med. 2020;172(7):445-452. doi:10.7326/M19-3075
4. Restivo V, Costantino C, Bono S, et al. Influenza vaccine effectiveness among high-risk groups: A systematic literature review and meta-analysis of case-control and cohort studies. Hum Vaccin Immunother. 2018;14(3):724-735. doi:10.1080/21645515.2017.1321722