Flu Shot Associated With Extra Benefits in Patients With Heart Failure

Two studies presented at Heart Failure 2016 and the 3rd World Congress on Acute Heart Failure held in Florence, Italy, hold good news for patients with heart failure (HF) who get flu shots.

Ju-Chi Liu, MD, PhD, of Taipei Medical University, Shuang Ho Hospital, Taiwan, and colleagues reported that influenza vaccination is associated with a lower risk of dementia in patients with HF. The study followed 20,509 patients over age 60 who visited healthcare facilities in Taiwan with a HF diagnosis from 2000 to 2012. Patients with dementia prior to being diagnosed with HF were excluded from the study. Of the 20,509 HF patients, 10,797 received at least one flu vaccination; the other 9712 were not vaccinated during the 12 years of follow up.

After adjusting for factors that could confound the results, the investigators found that HF patients who had gotten flu shots were 35% less likely to develop dementia than those who had not been vaccinated. Those who had been vaccinated more than 3 times had a 55% lower dementia risk.

The researchers also found that vaccinated HF patients over age 70 had a 44% lower risk of dementia and a 26% lower risk of dementia if they were 60 to 69 years old. Male HF patients had a 40% lower risk of dementia if they were vaccinated and female HF patients had a 31% lower dementia risk.

Liu noted that the flu virus is thought to activate the immune response and cause inflammation, which may injure brain cells. Respiratory infection during the flu infection can cause changes in blood pressure and heart rate, which may also harm brain tissue. HF patients already have impaired circulation, so the effects of the flu can play a role in dementia, Liu concluded.

The second study presented at the conference concludes that the flu shot is associated with a reduced risk of hospitalization in HF patients. Kazem Rahimi, FRCP, DM, MSc, FESC, of the George Institute for Global Health in Oxford, UK, and colleagues used the records of 4.9 million adults in the UK Department of Health’s Clinical Practice Research Datalink from 1990 to 2013 to assess the impact of flu vaccination on the risk of cause-specific hospitalization in HF patients. The risk of hospitalization for cardiovascular disease, respiratory disease, and all causes was compared between a year in which a patient was vaccinated and an adjacent year when they were not.

Investigators identified 59,202 HF patients in the database. Flu vaccination was associated with a 30% risk of hospitalization for cardiovascular diseases, a 16% lower risk of hospitalization due to respiratory infections, and a 4% lower risk of all-cause hospitalization in the period 31-300 days after vaccination compared with the corresponding period in an adjacent vaccine-free year.

Rahimi suggests that the reduction in risk of cardiovascular hospitalization occurs because vaccination reduces the likelihood of an infection that could in turn trigger cardiovascular deterioration. The observed associations between vaccination and hospitalizations were largest 31-120 days after vaccination, and in younger patients (less than 66 years old). But the absolute benefit is probably larger in older patients because they are at greater risk of hospital admission, Rahimi said.

The findings were validated by examining whether there was any association between flu vaccination and hospitalization due to cancer. As anticipated, there was no association, supporting the validity of the analysis.