Obesity and the flu

Obesity is a growing concern as rates nearly tripled worldwide between 1975 and 2016 to 650 million adults. Being very overweight is often seen as a factor in many health problems, but now is seen as a factor in people’s risk of getting, transmitting, and dying from influenza. Wait! What?

The Flu Shot is NOT as Effective

In a study published in 2017 by the International Journal of Obesity, scientists at the University of North Carolina at Chapel Hill found that the flu vaccine provides less protection in people who are obese. Nearly 10% of vaccinated obese participants got the flu, compared with 5% of their healthy-weight counterparts. The data suggested that even though antibody levels were the same in both groups, certain T cells were compromised. T cells are a type of white blood cell that’s essential for a healthy immune system. T cells support the protection and recovery from influenza, but these were much lower functioning in the obese individuals compared to the normal weight people. As a result, a 30-year-old obese person’s immune cells looked a lot like those of an 80-year-old.

A recent influenza field study, funded in part by the National Institute of Health (NIH) and the St. Jude Children’s Research Hospital Center of Excellence for Influenza Research and Surveillance (CEIRS), looked at the effect of obesity on the length of time people remained contagious. It was observed that, within households, obese people with symptoms carried transmittable virus in their mucous 42% longer than non-obese adults. And the high rate of possible transmission was present even when the study participants showed only minor symptoms. 

There was some good news from the study. Obese children and teens did not appear to shed or transmit influenza for any longer than non-obese children, but they are still likely to have a higher risk of catching the flu, and suffering a worse case of it.

Tracing the Problem to the Lungs

The St. Jude Department of Infectious Diseases’ laboratory studies on the obesity-influenza connection suggest that influenza virus may spread more quickly and deeper into the lung tissue of obese patients, making them at higher risk for pneumonia. Their compromised cells did not “see” the invading influenza virus soon enough to release antiviral interferons quickly, or they seemed to overreact causing too much inflammation. Researchers found that flu viruses in the obese replicated faster and required lower viral concentrations to be able to infect healthy cells more easily. Also, these infected cells took longer to heal their damaged membranes, which then left the lungs more vulnerable to a secondary bacterial lung infection. 

A ‘Moon Shot’ Universal Vaccine

St Jude Hospital and many infectious disease research centers are working to develop a more potent “universal flu vaccine.” The goal is a reliable vaccine that can address an expanding range of virus strains across all ages and sizes in the population. Lower T-cell immunity may also be why flu vaccines don’t work as well in older people, so improvements in the vaccine will help both the elder population as well as those who are overweight.

Clinical Trials 

The medical community is concerned that clinical trials to test new universal flu vaccines will likely be conducted only with a “healthy” population. Obesity normally disqualifies subjects from these kind of trials–which is a problem. Along with children and the elderly, this is the most vulnerable, and growing, at-risk population. 

Meanwhile everyone, big and small, should get an annual flu shot, which may also offer pneumonia protection. And remember to wash your hands!

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