Flu jabs do NOT stop fat people from contracting illness, doctors claim
Controversial study suggests vaccinations don't work if the person is carrying extra weight
Flu jabs do not protect fat people from catching a cold, a new study suggests.
Experiments in obese mice found vaccines do not work as well in obese bodies.
Obese animals were more susceptible to the virus, which penetrated more deeply into the lungs, making it harder to repair the damage caused.
Vaccines are the front line defence in combating flu epidemics and obese people are at increased risk of severe flu and complications including hospitalisation and death.
An estimated one in four adults and one in five children are obese in the UK with numbers expected to grow while there are fears of a future pandemic caused by bird flu or other strains that jump species.
Associate Member Dr Stacey Schultz-Cherry said: "This is the first study to show that current strategies to bolster the effectiveness of flu vaccines protected lean mice from serious illness but fell short of protecting obese mice from infections.
"There is a critical public health need to translate these findings to humans and understand vaccine response in this growing segment of the population"
The strategies include increasing the vaccine dose and adding substances called adjuvants to vaccines to boost the immune response.
The study by St. Jude Children's Research Hospital in Memphis, Tennessee, used vaccines prepared from killed viruses that are the basis of flu shots.
The vaccines targeted A H1N1 seasonal flu strain, the most common cause of flu in 2009 and associated with the 1918 outbreak known as the Spanish Flu, and bird flu strain A(H7N9).
Scientists looked at the immune response to vaccination in lean and obese mice, including how vaccine dose and different adjuvants impacted that response.
Both methods have been used to improve vaccine effectiveness in older adults and other high-risk groups by the team.
While adjuvants improved the immune response to vaccinations in both lean and obese mice, the overall immune response was reduced in the obese animals.
Following vaccination, the obese mice had lower antibody levels, including lower levels of neutralising antibodies, and higher levels of the virus.
Lean mice who received vaccines with adjuvants were protected from severe flu infections while obese mice were not.
Dr Schultz-Cherry in the Department of Infectious Diseases said: "The addition of adjuvants to the vaccines led to levels of neutralising antibodies in both the lean and obese mice that have been considered to be protective.
"Surprisingly that did not translate into protection from flu infection or fatal disease in the obese animals.
She added that suggested obese individuals may be at risk for flu infections even if their blood antibodies reach what have been considered protective levels.
A four-fold increase in the dose of A(H7N9) vaccine bolstered the immune response in both lean and obese mice, but failed to protect the heavier animals from flu-related deaths.
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Protective antibodies from lean mice also failed to protect obese mice from flu infections.
Staff scientist Dr Erik Karlsson in the Schultz-Cherry laboratory said: "That suggests the problem lies with the immune response of the obese animals rather than the antibodies themselves."
The obese mice seemed more susceptible to the virus, which remained elevated following vaccination compared to blood levels in lean animals.
Dr Schultz-Cherry said: "The virus penetrates more deeply into the lungs of obese mice, and the animals seem to have a more difficult time repairing the damage."
The study was published in the scientific journal mBio.
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