Vaccines Unsuccessful in Protecting Obese Mice Against Influenza Infections


A recent study published in mBio, a respected scientific journal, found that flu vaccines that include adjuvants were not effective at protecting obese mice from infection. Their findings suggest the vaccine may not be sufficient to protect obese humans, especially since they are also the most likely to experience severe flu symptoms.

One of the authors of the study is Stacey Schultz-Cherry, a member of the Infectious Diseases Department at St. Jude Children’s Research Hospital. She claims that the study is one of the first of its kind, and it shows how the most common methods of raising vaccine efficiency only benefit those who have healthy levels of body fat. Those strategies need to be changed if they hope to be effective at protecting obese individuals as well. As of now, the only methods used to increase efficiency are increased doses and the addition of adjuvants, which are substances used to boost immune system response.

Flu Vaccines and the Obesity Epidemic

There is a current level of rising fear associated with global levels of obesity, as well as concerns over new flu epidemics caused by new strains. It has been estimated by the World Health Organization that 10 percent of all adults in the world are overweight. Another 42 million children on top of that are also considered obese for their age. Anyone who suffers from obesity has an increased risk for complications that might arise due to the flu. Such risks include long-term hospitalization or, in the worst cases, death.

This new study has prompted new fears regarding the ability of the medical field to adequately vaccinate the obese members of the population. Vaccines are still the best tool against viral infections like the flu, and research institutions all over the world are working to make vaccines better. Most research groups focus on boosting the efficiency of existing vaccines for groups of people who need different forms of treatment, like pregnant women and the elderly. Obese people may need to be added to that list, if the results of this study prove to hold true for humans.

This particular study was conducted with basic flu vaccines that were targeted to a strain of the standard H1N1 seasonal virus. The study also included H7N9, which is another strain with potentially pandemic qualities. Researchers studied both lean and obese mice and measured their response to the vaccines. Their variables were the size of the dose and the adjuvants added to increase the impact of the vaccine.

The presence of the adjuvants in the vaccine caused the immune systems of both sets of mice to respond with higher levels of antibodies, but the total immune response in the obese mice was negative. Levels of the virus itself were raised in the obese mice, and they had lower levels of antibodies. The obese mice also did not have any protection against the more severe infections, but the lean mice did.

The surprising thing about the study is that it points to obesity being the direct cause of the difference in efficacy. Obese mice still reacted to the vaccination, and their blood still had what would be considered protective levels of the antibodies, yet the infections happened anyway. This suggests the immune response is diluted due to obesity.

Researchers attempted to transfer some of the antibodies from the lean mice to the obese mice. This was to determine if the problem was in the antibodies themselves. Perhaps the obese mice simply could no longer produce them correctly. However, the antibodies from the lean mice did nothing to protect the obese mice. That points toward a problem within the immune response of the animal, which is almost certainly directly caused by obesity.


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