COVID vaccines protect people of all body weights

In a recent study published in The Lancet, researchers in the United Kingdom determined whether a person with a higher body mass index (BMI) had a weaker immune response to a vaccine against coronavirus disease 2019 (COVID-19). In addition, they examined vaccine uptake and the risk of severe COVID-19 outcomes in such individuals.

Study: Associations of BMI with COVID-19 vaccine uptake, vaccine efficacy and risk of severe COVID-19 outcomes after vaccination in England: a population-based cohort study† Image Credit: GrooTrai/Shutterstock

Background

By 2021, approximately 82.5% of the United Kingdom (UK) population had received a regimen of two doses of COVID-19 vaccines. However, there is no information on the use of COVID-19 vaccination for the nine million British population stratified by BMI groups.

Studies have shown that the effectiveness of the flu vaccine is lower in individuals with a higher BMI. Since COVID-19 is also a respiratory infection; therefore, it is justified to investigate whether there is a relationship between BMI and the effectiveness of the COVID-19 vaccine (VE). In addition, the long-term evidence on a range of COVID-19 outcomes across all BMI groups is also needed, as it could demonstrate the need for alternative risk mitigation strategies and targeted vaccine booster programs for those at high risk.

About the study

In the current observational cohort study, researchers used the QResearch database of GP registries to identify individuals for whom BMI data was available and who had been vaccinated in England between 8 December 2020 and 17 November 2021. They calculated vaccine uptake as the fraction of individuals with zero, one, two or three vaccine doses across four BMI categories. The BMI categories were – underweight (<18.5kg/m²), healthy weight (18.5 to 24.9 kg/m²), overweight (25 to 29kg/m²) and obese (>30kg/m²† The study analysis took into account several demographic confounders, including age, gender, ethnicity, socioeconomic status, and relevant co-morbidities.

The team also examined VE against infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Furthermore, using a matched case-control design, they estimated the odds ratio (OR) for severe COVID-19 outcomes in vaccinated versus those who had not, taking into account vaccine dose and elapsed time. since vaccination. Finally, they estimated the risk of severe COVID-19 outcomes associated with BMI after vaccination using multivariable cox-proportional risk models.

Study findings

Of 9,171,524 participants, 5,666,461 were COVID-19 positive during the study duration. In the end, 32,808 COVID-19 positive participants were hospitalized and 14,389 died. Of all study participants, 19.2% had not been vaccinated. Of the remaining participants, 3.1%, 52.6% and 25% received one, two and three doses of vaccine, respectively. The mean age of the study participants was 52 years and the mean BMI was 26.7 kg/m².

Percentage of people who received none, one, two or three doses of vaccination by age and BMI group

Vaccination coverage was lower in underweight people than in overweight or obese people (70 to 83% versus over 80%). These individuals were 40 years of age or older and had received two or three doses of vaccine. In all four BMI groups, study results were significantly heterogeneous with regard to protection against severe COVID-19.

Accordingly, hospitalization ORs for underweight, normal weight, overweight and obesity were 0.51, 0.34, 0.32 and 0.32, respectively. Similarly, the ORs of COVID-19-related mortality for underweight, normal weight, overweight, and obesity were 0.60, 0.39, 0.30, and 0.26, respectively. Compared to unvaccinated subjects, hospitalization and death were higher after 14 days of the second vaccine dose in vaccinated subjects. Also in the vaccinated participants, the correlation between BMI and COVID-19 hospitalization and death was linear after the first and J-shaped after the second vaccine dose. The researchers observed an inverted U-shaped association between BMI and the third vaccine dose, indicating that a booster was needed to provide full protection to obese people.

In addition, the first and second sets of sensitivity analyzes used two different cohorts. The first set had individuals for whom the BMI records from two years prior to cohort enrollment were available. Their VE showed smaller ORs compared to the primary study analysis; however, the results of both sensitivity analyzes were generally consistent with key study findings.

Risk of serious consequences of COVID-19 after vaccination. Estimates of the risk after 14 days from each vaccine dose. Adjusted for age, calendar week, gender, ethnicity, socioeconomic status, region, smoking status, hypertension, type 1 diabetes, type 2 diabetes, cardiovascular disease, and nursing home status. COVID-19 hospitalizations after first dose (A), second dose (B), and third dose (C), and deaths from COVID-19 after first dose (D), second dose (E), and third dose (F).

conclusions

The current large population-based cohort study has shown that COVID-19 vaccines protect against serious diseases; however, of similar magnitude in both obese and normal-weight people. However, the VE was decreased for underweight individuals among those with lower vaccination coverage across all ages. In addition, the study results indicated a higher risk of developing severe COVID-19 in obese and underweight people in the vaccinated cohort because they had lower vaccine uptake and showed much reduced VE. Taken together, these results emphasized the need for concerted efforts to increase vaccination coverage in people with a BMI of less than 18.5 kg/m2.²† Creating awareness among people to maintain a healthy weight could indeed help reduce the burden of COVID-19.