Obesity may seriously undermine the effectiveness of the influenza vaccine, a new study finds. According to a report published in the International Journal of Obesity, obesity may undermine the body's ability to defend itself against the influenza virus.
The results of this study underscore the serious dangers obesity poses to a person's health and well-being.
Researchers from the University of South Carolina at Chapel Hill sought to determine immune system responsiveness to influenza vaccine in healthy weight, overweight and obese test subjects at one month and twelve months after vaccination. This study is the first time that scientists have investigated how obesity may impact antibody responsiveness to influenza vaccines.
To this end scientific investigators recruited 499 patients from the University of North Carolina Family Medicine Center to participate in a prospective observational study. All of the patients were scheduled to receive 2009 - 2010 seasonal flu vaccinations.
Obesity Is Associated With Weaker Immune Response To Flu Vaccine
Initially, body mass index (BMI) was positively correlated with increased antibody production i.e. higher BMI was associated with more antibody production, but after twelve months post vaccination, things began to change. Researchers observed a significant drop in antibody response in obese patients. In fact, one year after receiving the flu vaccine, obese patients had a four-fold drop in antibody responsiveness compared to healthy people.
This is very significant because flu vaccines are designed to expose the body to weakened strains of virus leading to production of antibodies that attack the weakened virus (think of antibodies as microscopic bullets). When someone comes into contact with a powerful strain of that virus, his/her immune system unleashes antibodies to kill it. If a person is unable to successfully fight off infection, they are likely to die.
Researchers also studied obesity's effects on white blood cells that help fight infection.
In normal situations, when people are exposed to infection (flu virus, in this case), they produce special cells that help the body mount a defense against the foreign invader. These cells have the ability to remember certain information about the virus.
When these cells reproduce through mitosis, they pass this vital information to their progeny. These daughter cells remember what the deadly intruder "looked" like and from that time onward, each geneneration will patrol the body making sure the virus doesn't return. If they encounter the virus again, they attack and destroy it, also signalling more cells to the site of infection.
In the University of North Carolina study, scientists noted that obese patients had lower percentages of CD8+T cells (those special memory cells that fight infection). This observation, along with the decreased antibody levels, suggests that obese people will be less capable of fighting off the flu than people whom are healthy weight.
Obese People May Be At Greater Risk For The Flu
The University of North Carolina study demonstrated that obesity impairs the immune system's ability to combat the flu. Upon observation of the decreased antibody levels and poor CD8+T cell response to flu vaccines in obese patients, research investigators wrote:"...[I]nfluenza vaccine antibody levels decline significantly and CD8+T cell responses are defective in obese compared with healthy weight individuals. These findings suggest a mechanism for the increased risk of severe disease from pH1N1 infection in the obese population."
It's important to remember these results are from an ongoing study, and more work must be done to determine the severity of the risk among the obese. However, based on the first two years of observation, there is strong evidence that obesity impairs the body's ability to fight disease - at least the flu.
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Sheridan, P A, Haich HA, Handy, J et al. Obesity is associated with impaired immune response to influenza vaccination in humans. International Journal of Obesity. doi: 10.1038/ijo.2011.208
"Influenza Vaccine May Be Less Effective For Obese People, Study" copyright 2011 Living Fit, Healthy and Happy(SM). All Rights Reserved.