ACC: Flu Vaccine Less Effective in Heart Failure Patients 3-31-08

CHICAGO, March 31 -- Heart failure patients may not have as strong an immune response to flu vaccine as healthy patients, researchers found.

Patients with heart failure had a significantly (P=0.017) lower antibody response to one of the three influenza virus strains found in the vaccine compared with healthy patients, Orly Vardeny, Pharm.D., of the University of Wisconsin in Madison, told attendees at the American College of Cardiology meeting here.

"We hypothesize that [the impaired response] has something to do with the pathophysiology of heart failure itself, meaning some neurohormone levels are increased, such as norepinephrine and angiotensin II," she said, "and we're specifically studying the effects of norepinephrine or beta-adrenergic mechanisms in vaccine responses."

Dr. Vardeny added, however, that patients with heart failure should not stop getting immunized on the basis of these findings.

"We're saying in fact that they should, but that maybe more preventative measures should be taken as well," she said.

She said that it has been previously established that heart failure patients were at an increased risk for developing influenza, which is why yearly vaccination is recommended for them.

But there are still high numbers of hospitalizations and deaths from influenza in heart failure patients, Dr. Vardeny said.

To explore this issue, Dr. Vardeny and colleagues examined the immune responses to the 2006-2007 influenza vaccine in 29 heart failure patients (nine ischemic and 20 nonischemic) and 17 healthy controls of similar age and gender.

The heart failure patients had all been stable on a drug therapy regimen for at least 30 days.

The researchers measured blood antibody levels to three influenza strains -- H1N1, B/Shanghai, and H3N2 -- and T-cell responses -- gamma interferon and IL-10 production -- before and then two to four weeks after immunization.

Heart failure patients had a significantly (P=0.001) greater increase in IL-10 production but similar gamma interferon responses compared with the healthy controls.

All patients showed seroprotection -- at least a four-fold increase in antibody production to at least one viral strain -- following immunization. Overall, heart failure patients had lower levels of seroconversion, but the difference from healthy patients did not reach statistical significance.

However, antibody response to H3N2, the newest strain added to the vaccine, was significantly (P=0.017) lower in patients with heart failure.

Antibody responses to the other two strains showed a trend toward being lower in heart failure patients than in healthy controls, but the differences were not statistically significant.

The H3N2 strain had not been included in any previous vaccines and, therefore, neither the heart failure patients nor the healthy controls had been exposed to it before this study.

The finding of an impaired immunological response to this strain in heart failure patients suggests that immunological memory is particularly important in conferring protection against influenza in these patients, said Dr. Vardeny.

These findings also imply that "heart failure goes beyond the heart, that there are other systems challenged by [the condition]," commented Janet Wright, M.D., a vice president for science and quality at the ACC, who moderated the session at which the results were discussed.