(NaturalNews) While flu vaccines are often particularly recommended for people suffering from heart failure, those people are less protected by the vaccine than the general population, according to a study conducted by researchers from the University of Wisconsin and presented at the meeting of the American College of Cardiology in Chicago.
"What we theorize is that heart failure as a condition leads to impaired immune function, which renders these patients less able to respond to the vaccine," researcher Orly Vardeny said.
The researchers took blood samples from 29 heart failure patients and 17 healthy controls both before and after injecting them with the 2006-07 flu vaccine. This allowed them to measure the levels of flu antibodies in their systems and assess their immune response.
Because influenza mutates so rapidly, flu vaccines contain different strains of the virus every year. The 2006-07 vaccine was designed to protect against the H1N1, B/Shanghai and H3N2 strains. The H3N2 strain had never before been included in a flu vaccine, and none of the participants had ever been exposed to it before.
The researchers found that while all patients showed an increase in antibody production after getting the vaccine, this response was slightly diminished in the heart failure patients. This difference, however, was not statistically significant.
The significant difference showed up in response to the newest (H3N2) strain, with heart failure patients responding less effectively.
"Patients with heart failure had a reduced response to the newest virus introduced to the vaccine, meaning they had an impaired immune response compared with healthy individuals," Vardeny said.
Vardeny hypothesized that heart failure might lead to reductions in levels of certain hormones that regulate the immune system, and said that the researchers are investigating these connections.
The study highlights the fact that "heart failure goes beyond the heart, that there are other systems challenged by [the condition]," said Janet Wright of the American College of Cardiology.