Story at a glance

  • More than two-thirds of Americans are overweight or obese.
  • The excess weight leads to changes in the person’s metabolism that negatively impact their immune system.
  • Researchers think this may explain a troubling phenomenon: Flu shots don’t work as well among the obese. Now, researchers are working on a new, improved version of the vaccine to make it more effective.

Millions get the flu every year, and getting the yearly flu vaccine is far and away the best way to protect against it. But medical researchers have discovered that for the more than two-thirds of Americans who are overweight or obese, the vaccine doesn’t seem to work as well, NPR reports

Health officials first noticed the pattern during the 2009 flu pandemic, when they observed that the disease was especially bad for those who were significantly overweight. For some reason, the virus was able to grow to higher concentrations in obese patients, even spreading deeper into their lungs, Stacey Schultz-Cherry, an infectious disease specialist at St. Jude Children's Research Hospital, told NPR. 

Besides getting people sicker, this also made them more likely to spread the disease, which is bad news for public health. When researchers studied the phenomenon more closely they found that the breath of obese patients contained more virus particles and that overweight people could spread the virus for an extra day, on average, compared to those with lower body weight. 

Now, researchers are trying to figure out why so they can make the flu vaccine more effective. 

Melinda Beck, a professor of nutrition at the University of North Carolina at Chapel Hill, is studying how obesity impacts the immune system. Being significantly overweight changes a person’s metabolism, which impacts a range of bodily functions and can hamper the immune system. When we get sick, proteins in our bloodstream called antibodies attack viruses, while other cells, called T cells, also help fight disease. These T cells are what fail in the case of obese patients, Beck told NPR. 

Beck has studied this phenomenon in mice and says the loss of T cell function is similar to what’s observed in the elderly. So, a "30-year-old obese person has the immune cells that look a lot like what you might expect in an 80-year-old individual," Beck told NPR. She thinks T cells could explain why the flu vaccine doesn’t work as well for significantly overweight people and the elderly. 

Schultz-Cherry is part of an effort to develop a new vaccine that will work better for these vulnerable groups. Developing this new flu shot is likely to take years, but Schultz-Cherry emphasized that this is no reason not to get the vaccine in the meantime, as it’s still our best chance of avoiding a disease that infected between 37 and 43 million people last flu season.

Published on Nov 27, 2019