A less effective vaccine for obese people

Several recent studies indicate that metabolic and immune disturbances caused by excess fat dramatically increase the risk of complications from COVID-19 and may even interfere with the effectiveness of a vaccine against this disease.

According to the World Health Organization, there were 650 million obese adults worldwide in 2016, three more than in 1975, and the percentage of adults suffering from obesity is predicted to exceed 50%. by 2050 (1).

These statistics are catastrophic, because obesity is directly responsible for several serious diseases that shorten healthy life expectancy, including type 2 diabetes, cardiovascular disease and several types of cancer.

In practice, the rise in the incidence of obesity is so great that it is completely canceling out the benefits obtained by the drop in the smoking rate over the past decades (2).

Obese at risk

In addition to promoting the development of these chronic diseases, the data collected since the start of the COVID-19 pandemic clearly shows that obesity considerably worsens the risk of complications associated with this disease. Compared to people of normal weight, a recent analysis (3) reports that obese people have:

• 46% more risk of being infected with the coronavirus.
• 113% more risk of being hospitalized.
• 74% more risk of being admitted to intensive care.
• 48% more risk of dying from the disease.

These increases in the risk of developing severe forms of Covid-19 are a direct consequence of the many metabolic upheavals that result from excess fat.

It should be remembered that obesity is first and foremost a totally abnormal physiological state, characterized by several imbalances in the metabolism, in particular insulin resistance, hyperglycemia and the development of chronic inflammatory conditions.

These imbalances have extremely serious effects on the functioning of the body and promote the development of a myriad of pathologies (hypertension, dyslipidemias, type 2 diabetes, kidney and liver diseases) which are all important risk factors for mortality. linked to COVID-19.

Immune disorders

Another negative aspect of obesity, less well known, is its negative impact on the immune system.

Studies show that being overweight disrupts the activity of certain regulatory cells involved in the rapid response to an infectious agent, which allows the virus to multiply without hindrance and to take a step ahead of immune cells.

When these finally reach the site of infection, the damage caused is already extensive and elicits a disproportionate response that will lead to the development of high-intensity inflammation that can damage nearby healthy cells and disrupt vital functions.

Since adipose tissue contains large amounts of inflammatory immune cells, this inflammation becomes chronic and interferes in the long term with the functioning of the immunity.

Less efficient vaccines

Another problem associated with this chronic inflammation is that it ends up depleting the resources of the immune system and thus decreases its ability to develop long term memory of the infection (in the form of antibodies and specific T cells). This immune amnesia therefore means that a possible anti-COVID-19 vaccine could prove to be less effective in obese people than in the general population.

This phenomenon has already been observed with the influenza vaccine: obese people are twice as likely to be infected with this virus and develop clinical signs of the disease than people of normal weight, even after being overweight. vaccinated (4).

In short, obese people must be aware that they are extremely vulnerable to COVID-19 and remain very vigilant to eliminate as much as possible any exposure to the virus, by applying public health measures to the letter.

(1) World Health Organization. 2020. Obesity and overweight. World Health Organization, Geneva, Switzerland. https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight.

(2) Stewart ST et al. Forecasting the effects of obesity and smoking on US life expectancy. N. Engl. J. Med. 2009; 361: 2252–2260.

(3) Popkin BM et al. Individuals with obesity and COVID-19: A global perspective on the epidemiology and biological relationships. Obesity Rev., published August 26, 2020.

(4) Neidich SD et al. Increased risk of influenza among vaccinated adults who are obese. Int. J. Obes. 2017; 41: 1324–1330.