Excess body weight can weaken efficacy of flu vaccine

Research indicates that the flu vaccine is less effective in obese individuals. A study from the University of North Carolina found that vaccinated obese adults have a higher risk of flu compared to those with healthy weight. During the 2009 flu outbreak, it was observed that the infection was more severe in overweight individuals, with the virus spreading deeper in the lungs. A University of Maryland study showed that more virus is exhaled by obese individuals. According to Professor Melinda Beck, excess weight causes metabolic changes that affect immune cells, leading to a reduced T cell response despite vaccination.

According to Professor Melinda Beck, how does excess weight affect the immune system?

What is the relationship between T cell function and flu infection in obese individuals despite vaccination?