Flu Vaccine May Offer Unexpected Health Benefits Aside from Immunity

Older adults who receive a flu shot have a 28 percent reduced risk of suffering a heart attack and are 17 percent less likely to develop Alzheimer’s disease, according to two new studies out of Texas. The research provides an even more compelling reason to get vaccinated for those on the fence about the shot’s effectiveness at preventing the seasonal flu.

The link between influenza infection and an increased risk of heart attack or stroke is relatively well-accepted within the medical community, with a 2018 study published in The New England Journal of Medicine reporting that patients over the age of 35 were six times more likely to experience a cardiac event in the first seven days after being diagnosed with an influenza infection. Fighting the flu puts a strain on the heart which is even more pronounced in people over the age of 50.

Despite this, researchers at Texas Tech University Health Sciences Center recently found that rates of flu vaccinations in vulnerable populations, such as those in long-term care homes, is discouragingly low.

“These groups should have the highest vaccination rates because they are the most at risk; however, our findings show the opposite – flu vaccinations are under-utilized,” said Roshni A. Mandania, BS, lead author of the study and MD Candidate at Texas Tech University Health Sciences Center Paul L. Foster School of Medicine in El Paso, Texas. “As healthcare providers, we must do everything we can to ensure our most vulnerable populations are protected against the flu and its serious complications.”

Led by Dr. Debabrata Mukherjee, chief of cardiovascular services at Texas Tech University Medical Center at El Paso, Mandania and colleagues presented the findings of their research at the virtual American Heart Association’s Basic Cardiovascular Sciences 2020 Scientific Sessions, held from July 27 to 30, 2020.

The team used patient data from the 2014 National Inpatient Sample to determine the percentage of high-risk patients who received the flu vaccine during hospitalization, and what effect getting the flu shot had on cardiovascular outcomes.

Flu Vaccine Reduces Heart Attack Risk

Out of a cohort of over seven million hospitalized patients deemed to be at a high risk of influenza infection due to age and the presence of preexisting conditions, just two percent received the flu vaccine. High-risk groups included in the study were less likely to be vaccinated, including patients 50 years and older, long-term care residents, individuals with HIV/AIDS and those considered to be obese.

While 15.3 percent of the general population received the flu vaccine that year, just 1.8 percent of adults age 50 and over were vaccinated. As with older adults, the same percentage of nursing home residents were vaccinated, while 9.5 percent of seniors living on their own got the flu shot.

But the benefits of getting vaccinated on heart health are hard to ignore – Mandania and colleagues observed an 85 percent reduced risk of cardiac arrest, 73 percent reduced risk of death, 47 percent reduced risk of transient ischemic attack (a type of stroke) and a 28 percent reduced risk of heart attack in those over 50 that had been vaccinated against the flu.

“The results we found are staggering. It’s hard to ignore the positive effect the flu vaccine can have on serious cardiac complications,” Mandania said. “Some people don’t view flu vaccinations as necessary or important, and many may face barriers accessing healthcare including receiving the flu vaccine.”

Incidence of Alzheimer’s Diagnosis and the Flu Vaccine

And if the cardiovascular benefits aren’t compelling enough to encourage more widespread acceptance of the flu vaccine, research led by Dr. Paul E. Schulz, Rick McCord Professor in Neurology and Umphrey Family Professor in Neurodegenerative Diseases at The University of Texas Health Science Center at Houston (UTHealth), has found that getting just one flu shot could reduce an individual’s lifetime risk of developing Alzheimer’s disease by 17 percent. These findings were also presented virtually at the 2020 Alzheimer’s Association International Conference, which was held concurrently with the American Heart Association’s conference.

“Because there are no treatments for Alzheimer’s disease, it is crucial that we find ways to prevent it and delay its onset,” said Albert Amran, a fourth-year medical student at McGovern Medical School at UTHealth. “About 5.8 million people in the United States have this disease, so even a small reduction in risk can make a dramatic difference. We began our study by looking for ways we could reduce this risk.”

Amran and colleagues stumbled upon the link between Alzheimer’s and the flu vaccine while searching through the Cerner Health Facts database, a large collection of de-identified patient data from more than 600 hospitals, for already-approved drugs that could also help prevent the degenerative neurological condition. In collaboration with Dr. Xiaoqian Jiang, an associate professor at UTHealth School of Biomedical Informatics, they analyzed over 300,000 electronic health records using machine learning and identified a relationship between receiving the flu vaccine and the incidence of Alzheimer’s diagnosis.

While the risk of developing Alzheimer’s was found to be lower for individuals who had received just one flu shot in their lives, those who were vaccinated at a younger age and for multiple years had even better protection from being diagnosed with dementia.

“One of our theories of how the flu vaccine may work is that some of the proteins in the flu virus may train the body’s immune response to better protect against Alzheimer’s disease,” Amran said. “Providing people with a flu vaccine may be a safe way to introduce those proteins that could help prepare the body to fight off the disease. Additional studies in large clinical trials are needed to explore whether the flu shot could serve as a valid public health strategy in the fight against this disease.”

The spread of COVID-19 has presented yet another reason to get the seasonal flu vaccine, with health agencies like the Centers for Disease Control and Prevention (CDC) urging people to consider that getting the shot can not only help protect their own health, but also ensure that healthcare resources are reserved for those most in need.

The composition of the seasonal flu vaccine is based upon which strains are dominant in Australia and other Southern countries where winter begins mid-year. According to the Australian Government’s Department of Health, their most recent Australian Influenza Surveillance Report has shown a lower-than-average level of influenza activity in the country, with cases decreasing since March. This year, most of the confirmed cases have been caused by influenza A, but the authority has reported that, “There is no indication of the potential severity of the 2020 season at this time.”