COVID-19 Vaccination Protects Against Severe Disease in Patients with Obesity


Vaccine effectiveness was slightly lower in patients with underweight, who also have the lowest levels of vaccine uptake across all ages.

Carmen Piernas, MSc, PhD

Carmen Piernas, MSc, PhD

New findings suggest a strong evidence of protection against severe COVID-19 in patients with overweight or obesity who have been vaccinated, at a similar magnitude to those who are considered healthy weight.

Among those individuals who were vaccinated, the findings suggest an increased risk of severe COVID-19 outcomes for individuals with underweight or obesity compared to the vaccinated population with a healthy weight.

“​​Despite the observed effectiveness of vaccination in people across all body mass index (BMIs), there were significantly higher risks of severe COVID-19 outcomes in vaccinated people with lower and higher BMIs than in people with a BMI of 23 kg/m², even after the second dose of the vaccine,“ wrote study author Carmen Piernas, MSc, PhD, Nuffield Department of Primary Care Health Sciences, Radcliffe Observatory Quarter, University of Oxford.

At the population level, a lack of data has been noted on COVID-19 vaccine effectiveness in patients with obesity. The current analysis used a large, representative population-based cohort of ≥9 million people in England to examine the associations between BMI and COVID-19 vaccine uptake, vaccine effectiveness, and risk of severe outcomes after vaccination.

Data from the Qresearch database of general practice records was collected, including individuals aged ≥18 years who were registered between December 2020 and November 2021 with ≥1 BMI measurement on record. Uptake of vaccines was calculated as the proportion of patients with zero, one, two, or three doses of the vaccine across BMI categories.

A total of 9,171,524 adults meeting inclusion criteria were included in the main analyses. From that population, a total of 566,461 tested positive for SARS-CoV-2 during follow-up, of which 32,808 were admitted to hospital and 14,389 were reported to have died.

Across the cohort, 19.2% (n = 1,758,689) were unvaccinated, 3.1% (n = 287,246) had one vaccine dose, 52.6% (n = 4,828,327) had two doses, and 25.0% (n = 2,297,262) had three doses. The uptake of two or three vaccine doses was reportedly more than 80% among individuals with overweight or obesity in ages 40 - 59 years, but slightly lower in patients who were underweight (70 - 83%).

Data show protection against severe COVID-19 comparing those who were vaccinated to those who were not was high after 14 days or more from the second dose for hospital admission (underweight: OR, 0.51 [95% CI, 0.41 - 0.63]; healthy weight, OR, 0.34 [95% CI, 0.32 - 0.36]; overweight, OR, 0.32 [95% CI, 0.30 - 0.34], and obesity, OR, 0.32 [95% CI, 0.30 - 0.34]).

It was additionally protective 14 days from the third dose (underweight, OR, 0.05 [95% CI, 0.36 - 0.98]; healthy weight, OR, 0.39 [95% CI, 0.33 - 0.47]; overweight, OR, 0.30 [95% CI, 0.25 - 0.35], and obesity, OR, 0.26 [95% CI, 0.22 - 0.30]).

“These results suggest the need for targeted efforts to increase uptake in people with low BMI (<18.5 kg/m²), in whom uptake is lower and vaccine effectiveness seems to be reduced,” Piernas concluded.

The study, “Associations of BMI with COVID-19 vaccine uptake, vaccine effectiveness, and risk of severe COVID-19 outcomes after vaccination in England: a population-based cohort study,” was published in The Lancet.

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