Data suggests that the Pfizer / BioNTech vaccine may be less effective in obese people.

Italian researchers found that healthcare workers suffering from obesity produced only about half the amount of antibodies in response to a second dose of the vaccine compared to healthy people. While it is too early to know what this means for the vaccine’s effectiveness, it could mean that people with obesity need an extra booster dose to make sure they are properly protected against it. the coronavirus.

Previous research has suggested that obesity – which is defined as having a body mass index (BMI) greater than 30 – increases the risk of dying from Covid-19 by almost 50%, as well as the risk of ending up in hospital by 113%.

This may be in part because people with obesity often have other underlying medical conditions, such as heart disease or type 2 diabetes, which increase their risk of coronavirus, but excess fat. The body can also cause metabolic changes, such as insulin resistance and inflammation, that make it harder for the body to fight infections.

This constant state of low-grade inflammation can also weaken certain immune responses, including those triggered by B and T cells that trigger a protective response after vaccination. Separate search has shown that the flu shot is only half as effective in obese people as it is in those at a healthy weight.

The new study, which has yet to be peer reviewed, provides the first direct evidence suggesting that a similar problem could arise with Covid-19 vaccines.


Aldo Venuti, from the Istituti Fisioterapici Ospitalieri in Rome, and his colleagues evaluated the antibody response after two doses of the Pfizer / BioNTech vaccine in 248 health workers. Seven days after receiving the second dose, 99.5% of them had developed an antibody response, and this response was greater than that recorded in people who had recovered from Covid-19. However, the response has been blunt in overweight and obese people.

“Since obesity is a major risk factor for morbidity and mortality for patients with Covid-19, it is mandatory to plan an effective vaccination program in this subgroup,” wrote Aldo and colleagues . “Although more studies are needed, these data may have important implications for the development of vaccination strategies against Covid-19, particularly in obese people. If our data were to be confirmed by larger studies, giving obese people an extra dose of the vaccine or a higher dose might be options to evaluate in this population.


“We’ve always known that BMI is a huge predictor of a poor immune response to vaccines, so this article is really interesting, although it’s based on a rather small preliminary data set,” said Danny Altmann, professor of immunology at Imperial College London. “This confirms that having a vaccinated population is not synonymous with having an immune population, especially in a country with high obesity, and underscores the vital need for long-term immune surveillance programs.”

In one separate study Brazilian healthcare workers, Altmann and colleagues have shown that reinfection with Sars-CoV-2 is also more common in people with high BMI and that they tend to have lower antibody responses to infection original.