Switching obese mice to a lower-fat diet before flu vaccination, but not afterwards, improves their ability to fight the virus. This suggests the flu shot may be more effective in people with obesity if they lose weight or eat a different diet beforehand.
Even with immunisation, people with obesity are to get the flu than those without it. They are also more vulnerable to severe cases of the illness. But why obesity seems to blunt vaccine efficacy 鈥� and how to prevent this effect 鈥� is unclear, says at St. Jude Children鈥檚 Research Hospital in Tennessee.
So she and her colleagues fed 20 mice genetically predisposed to developing obesity a high-fat diet for four months. They then inoculated the now-obese rodents against the flu. Two weeks later, they put half of the mice on a low-fat diet for a month, which led to significant weight loss. Afterwards, the animals were infected with a lethal dose of influenza virus. All of the mice died, except for two in the low-fat diet group.
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The team then repeated the experiment in a separate group of mice, but this time half of the rodents went on a low-fat diet a month before vaccination instead of afterwards. When the researchers infected the animals with the same amount of influenza virus, all of those on the low-fat diet survived, whereas none of those on the high-fat diet did. This indicates that 鈥渨eight loss can impact the effectiveness of the vaccine, but the timing of the weight loss makes a very big difference鈥�, says Schultz-Cherry.
However, further research must disentangle whether it was diet or weight loss that led to these improvements, says at the University of Southampton in the UK. Only then can we find ways to improve vaccine efficacy in people with obesity, she says.
鈥淚 think we have to be very careful about translating these findings to humans too,鈥� says Schultz-Cherry. For instance, a month for mice is equivalent to years for a human, she says.
Nature Microbiology
