Flu Shot and Obesity

A study from the University of North Carolina at Chapel Hill found that obesity may interfere with the body’s ability to mount a sufficient immune response to influenza virus, making the flu vaccine less effective. Influenza is a serious health threat, killing roughly half a million people worldwide each year. With the growing obesity rates in America, we could see more and more serious effects, including death, from complications of the flu.

Researchers noticed that during the H1N1 flu outbreak in 2009, obese individuals seemed to be affected by the virus more than those of normal weight.  The research team at Chapel Hill set out to determine how the immune response to the flu vaccine differs by Body Mass Index (BMI). They found that in comparison to healthy weight people, vaccine antibody levels decline significantly in obese people. About half of the obese people studied had a four-fold drop in antibody levels at one year compared to one month after vaccination.  In comparison, less than 25 percent of healthy weight participants had a four-fold decrease in antibody levels. Furthermore, the responses of CD8+ T cells (which are a type of white blood cell central to the body’s immune system) are defective in obese people, making them more likely to become sicker and have more complications from the flu.

Previous studies conducted by the research team found that obesity in mice interfered with their ability to fight the flu with a higher incidence of death from the flu in comparison to leaner mice. Obese mice had a fatality rate of about 25 percent, while there were no fatalities among the lean mice.  The new study indicates that obesity in humans may cause a similar impaired response to influenza vaccines as with the mice infected with the flu.

Dr. Laura Machado, expert bariatric surgeon and Medical Director of Sacramento Bariatric, spoke with us about the study, explaining that the findings expand on our knowledge regarding the negative impact of obesity on immune system function.  She said: “Obesity is a disease which has far reaching effects, not only with daily management of common disease states such as diabetes and hypertension, but long-term consequences that can impair our ability to fight disease. We already have evidence that those who suffer from obesity have increased rates of some of the most common cancers.  Part of this increase is related to a dysfunction of our immune system that detects abnormal cells and stops their division before it gets out of control.   We now have further information that the immune system is also compromised in obesity with regard to the effectiveness of vaccines.”

“Anecdotally, as a bariatric surgeon, I can recall a number of patients commenting on their improved health following weight loss and that they “cannot recall the last time they had a cold”.  This research continues to support the importance of effective obesity treatments.  Globally, obesity affects every country and indirectly could contribute to elevated risks and death rates from influenza outbreaks,” she concluded.

Additional Reading

Obesity is a risk factor for several serious health conditions and diseases.  As Dr. Machado explained, obese individuals are at an increased risk for several types of cancer. An article published earlier this year compared obesity to smoking, in terms of its relationship to cancer. You can read more about the link between obesity and cancer here.

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