Flu vaccines don’t work as well on the obese

The obese get significantly less protection from influenza vaccines than those at a more normative weight, even though those with excess weight are at higher risk for possibly fatal complications from the viral respiratory infection.

This was shown true on obese mice in studies led by researchers at St. Jude Children’s Research Hospital in Memphis, Tennessee. They included scientists from Ben-Gurion University of the Negev in Beersheba.

Flu vaccines with adjuvants (agents that change the effect of other agents in a vaccine to modify the immune response, by boosting it to make more antibodies and longer-lasting protection) were found not to work as well in very overweight rodents, thus highlighting the urgent need to understand vaccine response in obese humans.

A study was led by Dr. Stacey Schultz-Cherry, an infectious disease expert at St. Jude’s. It included Dr. Tomer Hertz of the National Institute for Biotechnology in the Negev, and the Shraga Segal department of microbiology, immunology and genetics in the Faculty of Health Sciences at BGU.

Their study was published last week in the journal mBio.

They found that obese mice are not protected against influenza infections by vaccines that include adjuvants, raising concerns about vaccine effectiveness in obese humans who are known to be at an increased risk for severe flu.

“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,” said Schultz-Cherry.

The strategies include increasing the vaccine dose and adding adjuvants to boost the immune response.

The findings come amid ongoing concerns about flu pandemics launched by avian flu viruses, and the global rise of obesity. The World Health Organization estimates that around the world, 10 percent of adults and 42 million children under the age of five now qualify as obese.

“There is a critical public health need to translate these findings to humans and understand vaccine response in this growing segment of the population,” Schultz-Cherry said.

Vaccination remains the most effective flu prevention strategy and a key element in pandemic flu preparedness.

The study used vaccines prepared from dead viruses, which are the basis of flu shots. The vaccines targeted A(H1N1), a seasonal influenza strain, as well as A(H7N9), a virus considered to have the potential to trigger a human pandemic.

Researchers 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.

While adjuvants improved the immune response to vaccinations in both lean and obese mice, the overall immune response was reduced in the obese animals compared to their lean counterparts. Following vaccination, the obese mice had lower antibody levels, including lower levels of neutralizing antibodies, and higher levels of the virus. In addition, skinny mice that were given vaccines with adjuvants were protected from severe flu infections, but overly fat mice were not.

“The addition of adjuvants to the vaccines led to levels of neutralizing antibodies in both the lean and obese mice that have been considered to be protective.”

Source: The Jerusalem Post, 9th August 2016.

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