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Pfizer vaccine may be less effective for obese people, study suggests

Researchers say obese people may require a different vaccination strategy

Photo (c) Karl Tapales - Getty Images
Obesity may weaken the efficacy of the Pfizer/BioNTech COVID-19 vaccine, new data suggests. 

A team of researchers in Rome found that obese people who had received two doses of the vaccine produced only about half the number of antibodies in response. The scientists defined “obese” as having a body mass index (BMI) over 30. 

The study looked at the effect of the vaccine on 248 health care workers seven days after they had received their final dose. Among those people, 99.5 percent developed an antibody response. However, the number of antibodies generated was hampered in people who were overweight and obsese. 

“Since obesity is a major risk factor for morbidity and mortality for patients with Covid-19, it is mandatory to plan an efficient vaccination programme in this subgroup,” wrote researcher Aldo Venuti. 

Venuti and his colleagues said more research is needed to determine whether overweight and obese people may require a different vaccination strategy, such as an additional booster dose or a stronger dose.

“Although further studies are needed, this data may have important implications to the development of vaccination strategies for COVID-19, particularly in obese people. If our data was to be confirmed by larger studies, giving obese people an extra dose of the vaccine or a higher dose could be options to be evaluated in this population.”

Studying the impact of obesity

An earlier study found that obesity can raise the risk of dying after contracting COVID-19 by nearly 50 percent. Obesity has also been found to increase the risk of being hospitalized due to the virus by 113 percent. 

Experts have pointed out that a key limitation of the current study is its small sample size. 

"We always knew that BMI was an enormous predictor of poor immune response to vaccines, so this paper is definitely interesting, although it is based on a rather small preliminary dataset," Danny Altmann, a professor of immunology at Imperial College London, told The Guardian. "It confirms that having a vaccinated population isn’t synonymous with having an immune population, especially in a country with high obesity, and emphasises the vital need for long-term immune monitoring programmes."

The report was published on the pre-print server Medrviv and has not yet been peer reviewed. 

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