Colds and flu

26 October 2011

Obesity makes flu shot less effective

The various health risks associated with being overweight or obese are well known, but a new study suggests this extra weight may also make your annual flu shot less effective.


A study found that antibody levels dropped more over time among those who weighed more.

The various health risks associated with being overweight or obese are well known, but a new study now suggests that this extra weight may also make your annual flu shot less effective.

What's more, obese and overweight people may be at higher risk for more severe illness if they do catch the flu, according to the findings published online in the International Journal of Obesity.

Flu vaccines work by causing protective antibodies to develop in the body. In the study obese, overweight and healthy weight individuals all developed antibodies to flu viruses within the first month after vaccination, but the antibody levels in the blood waned more rapidly among obese and overweight individuals.

Decrease in antibody levels

Specifically, there was a fourfold decrease in antibody levels 11 months after vaccination in half of the obese patients, compared to one month post-vaccination. By contrast, less than 25% of healthy weight participants showed this degree of decrease in their antibody levels after 11 months, the researchers found.

In addition, a type of white blood cell called CD8+ T-cells, which play a key role in priming the body's immune system, doesn't work properly in heavier people. When vaccination doesn't stave off the flu, people must rely, in part, on these white blood cells to limit the spread and severity of the infection.

"Over time, overweight and obese people are not maintaining their antibody levels to the extent that healthy weight people are," said study author Heather A. Paich, a graduate student at the University of North Carolina at Chapel Hill. "They also appear to have difficulty fighting the flu infection when it does occur."

Obesity linked to lower immunity

Whether or not obese or overweight individuals are more susceptible to the flu remains to be seen, she said.

"It has been well-documented that obesity is linked to lowered immunity, and I always urge my obese patients at any age to get flu shot," said Dr Neil Schachter, a professor of pulmonary medicine at Mount Sinai School of Medicine in New York City.

The fact that their response to the flu shot is impaired has significant clinical implications, he said. "They may be candidates for the double flu shot approach that we give to elderly patients – one shot in early fall and another in January," he said. "This may offer better protection for obese patients to avoid the flu or at least reduce the severity of the infection and reduce the risk of complications."

Two shots

Dr Louis Aronne, founder and director of the Comprehensive Weight Control Program at New York-Presbyterian Hospital/Weill Cornell Medical Centre in New York City, said that overweight and obese people may represent another group of people who are at high risk for flu and flu-related complications. He said more study is needed to see if these people would benefit from two shots, instead of one.

The bigger picture here is that there needs to be a medical specialty dedicated to caring for people who are obese, said Dr Scott Kahan, an obesity expert at Johns Hopkins University in Baltimore.

"Dosages of certain medications often have to be changed based on weight and, in this case, the flu vaccine dosage, or administration may need to be changed," he said. "It may also be that we need enhanced prevention or other adjunctive strategies in addition to the vaccine for flu protection among people who are overweight or obese," Kahan added. These issues are apparent in the treatment or prevention of other diseases and conditions as well.

(HealthDay News, October 2011) 

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Dr Heidi van Deventer completed her MBChB (Bachelor of Medicine and Bachelor of Surgery) degree in 2004 at the University of Stellenbosch.
She has additional training in ACLS (Advanced Cardiac Life Support) and PALS (Paediatric Advanced Life Support) as well as biostatistics and epidemiology.

Dr Van Deventer is currently working as a researcher at the Desmond Tutu Tuberculosis Centre at the University of Stellenbosch.

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