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Obesity Links to Faster Fading of COVID Vaccine Protection

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Researchers published the study covered in this summary on as a preprint that has not yet been peer reviewed.

Key Takeaways

  • The study results suggest that obesity may accelerate waning of antibody response to SARS-CoV-2 vaccination and increased breakthrough infections with COVID-19.

  • The findings documented evidence of reduced neutralizing antibody capacity 6 months after primary vaccination in people with severe obesity.

  • This was a large study involving about more than 3.5 million people who had received at least two doses of COVID-19 vaccine, including more than 650,000 with obesity.

Why This Matters

  • Obesity is associated with comorbidities that independently increase the risk for severe COVID-19, including type 2 diabetes, chronic kidney disease, and heart failure.

  • The authors concluded that additional or more frequent booster doses are likely to be required to maintain protection among people with obesity against COVID-19.

Study Design

  • Prospective longitudinal study of the incidence and severity of COVID-19 infections and immune responses in a cohort of more than 3.5 million adults from a Scottish healthcare database who received two or three doses of COVID-19 vaccine. The data came from the EAVE II study, centered at the University of Edinburgh.

  • About 16% had obesity with a body mass index of 30-39.9 kg/m2, and an additional 3% had severe obesity with a BMI of 40 kg/m2 or greater.

  • Although not specified in this preprint, another report from the EAVE II study said that the vaccines administered in Scotland have been the Pfizer-BioNTech and Oxford-AstraZeneca formulations.

Key Results

  • Between September 14, 2020 and March 19 of this year, 10,983 people (0.3% of the total cohort; 6.0 events per 1000 person-years) had severe COVID-19, consisting of 9733 who were hospitalized and 2207 who died (957 of those hospitalized also died).

  • People with obesity or severe obesity were at higher risk of hospitalization or death from COVID-19 after both a second and third (booster) dose of vaccine.

  • Compared with those with normal weight, those with severe obesity (BMI higher than 40) were at significantly increased risk for severe COVID-19 after a second vaccine dose, with an adjusted rate ratio 1.76, whereas those with standard obesity (BMI 30-40) were at a modestly but significantly increased risk with an adjusted rate ratio of 1.11.

  • Breakthrough infections after the second dose for those with severe obesity, obesity, and normal weight occurred on average at 10 weeks, 15 weeks, and 20 weeks, respectively.

  • Interaction testing showed that vaccine effectiveness significantly diminished over time across BMI groups, and protection waned more rapidly as BMI increased.

  • Results from immunophenotyping studies run in a subgroup of several dozen subjects with severe obesity or normal weight showed significant decrements in the robustness of antibody responses in those with severe obesity 6 months after a second or third vaccine dose.


  • The authors did not specify any limitations.


  • The study received no commercial funding.

  • One author received funding from Wellcome.

This is a summary of a preprint research study , “Accelerated waning of the humoral response to SARS-CoV-2 vaccines in obesity,” published by researchers primarily at the University of Cambridge, United Kingdom, on medRxiv, provided to you by Medscape. This study has not yet been peer reviewed. The full text of the study can be found on

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