A very interesting discovery links leptin, the main satiety hormone, to the effectiveness of vaccines.

According to the study authors, a team of Chinese researchers from the Universities of Shanghai and Hong Kong , having low leptin levels reduces the response to vaccines. And consequently it limits their effectiveness.

The response to vaccines depends on the metabolism

Healthy individuals with a good body weight have a longer and more efficient antibody response following the vaccine precisely because they have good leptin levels. Conversely, those with low leptin levels or a condition known as leptin resistance will be less effectively covered by the vaccine.

The researchers conducted the study on subjects who had vaccinated for influenza and hepatitis B, and found that there were inter-individual differences in the effectiveness of vaccines that could be explained by their leptin levels.

The objective of the study was in fact to understand the mechanisms by which vaccines are less effective for certain individuals than in others: these individuals have a lower antibody response.

For example, in the flu vaccine, the younger ones have coverage ranging from 70 to 90%, in the older ones it is 17 to 53%. This difference is caused by the activity of Tfh cells, the follicular T helper cells.
These cells have long been studied for their role in the immune process, as they promote the activity of B lymphocytes and the production of antibodies.

But what does the satiety hormone have to do with helper T cells?

Well, for years we have known that metabolism influences the immune response: those who have a good metabolism essentially have better immune defenses and when vaccinated they produce antibodies more easily.

In the study, published in the journal Nature , the researchers analyzed various metabolic parameters to understand how they influenced the antibody response to vaccines. It was found that leptin promotes the differentiation of follicular T helper cells and supports their immune reaction following vaccination.

Therefore, low leptin levels in a subject will be the signal that the vaccine will have poor efficacy.

To test their hypothesis, the researchers analyzed the leptin levels of those who had been vaccinated. They first divided people into different groups based on their antibody response to the trivalent influenza vaccine.
They found low leptin levels in those who had had little or no immune response after the vaccine.

Then they did the opposite. That is, they grouped the vaccinated subjects based on their leptin levels and not their antibody response.
And in those with low leptin levels, the vaccine had little effect, with little or no antibody production. The lowest levels of leptin belonged to those who did not have antibody production, ie who were unresponsive to the vaccine.

The study was then also done on mice to observe the mechanisms of action on leptin. These results again confirmed the researchers’ hypotheses.

They also want to use this discovery in the vaccination campaign against Covid, trying to boost the production of T helper cells in subjects with low levels of leptin to increase the effectiveness of the vaccine coverage.