Influenza vaccination and older hospitalized adults with cardiovascular disease: what are the benefits?

A study published in the International Journal of Infectious Diseases found that flu vaccines reduced in-hospital deaths and recurrent hospital admissions for elderly hospitalized patients with cardiovascular disease.

Yuangmu Huang, MD, assistant professor and associate researcher at Peking University School of Public Health in Beijing, China, and colleagues conducted the study.

Influenza causes between 291,000 and 646,000 deaths a year worldwide, according to the study authors.1 Older adults are at higher risk, but there is little evidence of how vaccination affects hospitalizations for adults with cardiovascular disease (CVD). Huang and colleagues said randomized controlled trials have provided some insight into positive effects, and observational studies have shown the ability to collect real-world data.2,3,4 “These studies have enabled the evaluation of influenza vaccination across a broader range of diseases and in individuals with broader demographics,” the 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 hospitalized adults aged ≥ 60 years with CVD.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 patients’ vaccination status. They used logistic regression with generalized estimating equations adjusted for unmeasured contributors to see whether the flu shot affected repeat hospitalization rates and hospital mortality.1

The researchers found that only 13.3% (95,060) of older adults hospitalized for cardiovascular disease had received a flu vaccine, while 618,428 (86.7%) were unvaccinated.1 Vaccinated patients tended to be female, older, had fewer inpatient visits, and fewer comorbidities. The researchers said vaccinated patients were also less likely to have had an alcohol-related diagnosis and were more likely to have had surgery.

Researchers reported that during the flu season for this study from 2013 to 2019, 7822 of the study patients with CVD died.1 There were 110,180 repeat hospitalizations: 69,459 related to cardiovascular disease and 7,909 to respiratory disease.1 “During the summer months, 3,555 patients with cardiovascular disease died and 23,843 had repeated hospitalizations (14,586 for cardiovascular disease, 1,276 for respiratory disease),” the authors said.1

Huang and colleagues reported that the risk of in-hospital death for patients with cardiovascular disease was reduced by 15% in the fitted model (odds ratios 0.85 [0.74, 0.99]).1 This association was stronger in patients with ischemic stroke (19%, odds ratio 0.81 [0.60, 1.06]).1 The number of deaths from hemorrhagic stroke decreased by 13% (odds ratio (0.87 [0.60, 1.27]).1 The researchers found that the confidence intervals were wide because of the small 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 combined influenza and pneumococcal vaccinations,” the authors noted.

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

“Our results add to the evidence base supporting the recommendation of annual influenza vaccination in older adults. Comprehensive interventions are needed to improve influenza vaccination coverage in older adults hospitalized for cardiovascular disease to prevent unwanted hospitalizations,” the researchers concluded.

references

  1. Pang Y, Liu X, Liu G, et al. Efficacy of influenza vaccination on in-hospital death and repeat hospital admissions in older adults with cardiovascular disease [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 to prevent influenza in the elderly. Cochrane Database System Rev. 2018;2(2):CD004876. Published February 1, 2018. 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. Efficacy of Influenza Vaccines in High-Risk Groups: A Systematic Literature Review and Meta-Analysis of Case-Control and Cohort Studies. Hum Vaccine Immunother. 2018;14(3):724-735. doi:10.1080/21645515.2017.1321722

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