Influenza vaccination linked to fewer CV, respiratory hospitalizations in patients with HF

Influenza vaccination was associated with a 30% reduction in CV hospitalization in patients with HF, according to recent study data.

Use of the influenza vaccine also was associated with a 16% reduction in hospitalization for respiratory disease in the cohort of 59,202 patients with HF (mean age, 75 years; 50% men), researchers found.

Kazem Rahimi, DM, MSc , FRCP, FESC , deputy director of The George Institute for Global Health, University of Oxford, and colleagues investigated whether influenza vaccination would reduce adverse events in patients with HF. Because a randomized controlled trial would present practical and ethical challenges, they conducted a review of patient records from the U.K. Department of Health’s Clinical Practice Research Datalink, analyzing patients diagnosed with HF who had at least 1 year with influenza vaccination and 1 year without it between 1990 and 2013.

Rahimi presented the results at Heart Failure 2016 and the 3rd World Congress on Acute Heart Failure in Florence, Italy.

“Uptake of the flu vaccination in [patients with HF] is relatively low, ranging from less than 20% in low- and middle-income countries to 50% to 70% in high-income countries like the U.K.,” Rahimi said in a press release. “This may be partly because there is no strong evidence to support the recommendation in these patients. In fact, there is limited evidence to suggest that vaccination may be less effective in [patients with HF] than in the general population because of their blunted immune response.”

For each patient, Rahimi and colleagues analyzed a vaccination year with an adjacent vaccination-free year, comparing 30-day exposure periods and calculating incidence rate ratios.

Vaccination resulted in an overall reduction in CV hospitalization (incidence RR = 0.7; 95% CI, 0.66-0.74), with the strongest effect coming in the first 30 days (incidence RR = 0.47; 95% CI, 0.39-0.57) and lessening with each subsequent 30-day period.

Vaccination was associated with a 16% overall reduction in hospitalization for respiratory infection (incidence RR = 0.84; 95% CI, 0.78-0.9), with the strongest effect coming in 30 days but losing significance after 120 days, according to the researchers.

There was a modest overall effect of vaccination on all-cause hospitalization (incidence RR = 0.96; 95% CI, 0.95-0.98), Rahimi and colleagues found.

Less than 10% of the cohort was vaccinated in 1990, a rate which rose to approximately 60% in 2001 and fell to approximately 50% in 2013.

“These findings do not suggest that influenza infection causes [MI] or other [CV] events,” Rahimi said in the release. “A more likely explanation for the reduction in risk of [CV] hospitalization is that vaccination reduces the likelihood of infection, which could in turn trigger [CV] deterioration. The relative effect seems to be smaller for respiratory infections, which may be due to the fact that the vast majority of these hospitalizations are not related to influenza, and in our study we were not able to distinguish between the different types of respiratory infection.”

Because the study was not a randomized controlled trial, residual confounding cannot be ruled out, but “the findings do provide further evidence that there are likely worthwhile benefits and on that basis, more efforts are needed to ensure that [patients with HF] receive an annual flu jab,” Rahimi said in the release. – by Erik Swain

Reference:

Rahimi K, et al. Late Breaking Clinical Trials III: Focus on Trial Updates, Registries and Meta-Analyses. Presented at: Heart Failure 2016 and the 3rd World Congress on Acute Heart Failure; May 21-24, 2016; Florence, Italy.
Disclosure: Rahimi reports no relevant financial disclosures.