Scientists know why COVID-19 vaccines do not work for everyone

Only vaccination can put an end to COVID-19 pandemic. Currently approved vaccines are highly effective and yet people's vaccine response sometimes is all over the place. Why is that? A new study from the University of Queensland linked a metabolic hormone known as leptin to poor vaccine antibody responses in the general population.

COVID-19 vaccines are highly effective, but not for everyone. Image credit: Kyna De Castro via Wikimedia

People seem to be really concerned about the side effects of vaccines. Usually a strong adverse response to a vaccine is very rare. However, scientists are more worried about inadequate protection from COVID-19 that some people seem to acquire after getting a vaccine. Researchers in Australia investigated several cohorts' responses to the influenza vaccine or hepatitis B vaccine pre-COVID and found a link between the metabolic and immune systems which could explain strange responses to vaccines.

Scientists employed multiple advanced techniques in immunology, genetics and biochemistry in this study and found that a metabolic hormone known as leptin directly promotes the development and function of cells used in immune response. In essence, the reduction of leptin compromises vaccine responses in both young and older individuals. There are ways to determine the levels of leptin, which would be helpful in predicting whether the vaccine is going to generate a proper antibody response.

Leptin is mostly produced by the fat tissue. This, of course, means that malnourished people have reduced levels of leptin and it compromises vaccine responses. Interestingly, obese people often have high levels of leptin and still often face  a poorer vaccine response. Scientists are still looking into it, but it is likely that it is caused by leptin resistance.

Healthy people have much better chances of being properly protected by a vaccine. They are already less likely to die from COVID-19, but vaccines provide even stronger protection. Professor Di Yu, lead author of the study, said: "Vaccines have been known for a very long time to have a different efficacy for individuals. Although our genetics partially contribute to the difference, other factors are also essential. When we are fit and healthy, we have a much better vaccine efficacy."

COVID-19 is still a new problem for us. And vaccination is also a relatively new process. This all means that we are still figuring some things out. Hopefully vaccines will work and we will soon see the end of COVID-19 pandemic. Maybe even more importantly we have to hope that the lessons we learned will stay with us for the upcoming pandemics.


Source: University of Queensland
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