In addition to age, obesity is the main risk factor for poor outcomes from COVID-19 (hospitalization, need for critical care, death). We already know from earlier studies that certain vaccines, such as those against influenza, hepatitis B, and rabies, are less effective in people with obesity. However, these studies defined obesity by body mass index (BMI). In fact, BMI does not take into account the amount and distribution of body fat. This can vary among people with the same BMI. Recent research suggests that more severe COVID-19 disease occurs in adults where their obesity is central. This means a person stores excess fat around their stomach rather than other parts of their body. This is also known as “abdominal obesity.”

Stomach fat may affect effectiveness of Pfizer vaccine

In a new study, Italian researchers measured the immune response to the Pfizer vaccine over time. They looked at over 1,000 healthcare workers who also had their waist measured to assess their abdominal obesity. They compared immune response (antibody levels) before and after two doses of the Pfizer vaccine in participants with and without abdominal obesity. Researchers took blood samples before the first vaccine dose and 21 days after the first vaccine dose. They also tested blood 1 and 3 months after participants received their second shot. Abdominal obesity was defined as a waist measurement above 94 cm in men and 80 cm in women.

Lower antibody levels linked to large waist measurements

Between the first and third month after the second vaccine shot, people with abdominal obesity had a greater drop in antibody levels compared to those without abdominal obesity. Specifically, for those with abdominal obesity, they had a lower antibody peak. Also, they had a more significant drop in antibody levels at three months. Their antibody responses were also much lower if they had never previously been infected with COVID compared to those with previous infection who also received just one vaccine dose.

People with abdominal obesity are at higher risk

This is most likely due to the fact that people with abdominal obesity tend to have higher long-term inflammation in their bodies because of the excess fat. We know that this compromises the immune system. In conclusion, people with abdominal obesity are at higher risk of having weaker antibody responses after receiving the COVID-19 vaccines. However, it remains to be seen whether people with abdominal obesity have more severe complications from COVID-19.


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