New research has shown that the flu jab may not work for overweight people.
Experiments have found the vaccines protected lean mice against viruses but did not work on rats that were of a bigger size.
Overweight animals are more susceptible to the virus, and it penetrated more deeply into their legs, making it harder to repair the damage caused.
The wings have raised concerns over the vaccine in obese humans who are already at a higher risk of suffering flu.
The World Health Organisation estimates that globally, 10 percent of adults and 42 million children under five, now qualify as obese.
The lead author of the report Dr Stacey Schultz-Cherry of St Jude Children’s Research Hospital said ‘’’This is the first study to show that current strategies to bolster the effectiveness of flu vaccines protected lean mice from a 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 them, which enhance the body’s immune response.
The study was published in the scientific journal mBio.