COVID-19 vaccine protects people of all body weights from hospitalization and death

COVID-19 vaccines greatly reduced the number of cases of severe COVID-19 disease for everyone regardless of their body size, according to a new study published in The Lancet Diabetes & Endocrinology. Vaccine effectiveness was similar for those with a higher BMI and of a healthy weight, but slightly lower in the underweight group, who were also the least likely to have been vaccinated.

In a further analysis of vaccinated people only, among the fewer COVID-19 cases recorded, people of very low and very high BMI were more likely to experience severe disease than vaccinated healthy weight people. This replicates the findings seen in a previous analysis before the vaccination programme commenced.  

Researchers searched anonymised health records from more than 12 million patients across 1,738 GP practices in England taking part in QResearch-a secure database of healthcare information available to verified researchers. Of these, 9,171,524 patients who were over 18 years old, had BMI data, had not previously been infected with SARS-CoV-2 were included in the study.

People were grouped based on their BMI according to four World Health Organisation definitions of 18.5-24.9kg/m2 for healthy weight; below 18.5 for underweight; 25-29.9 for overweight; and 30 and over as obesity with levels adjusted for Asian people to reflect the higher health risks at lower BMI levels in this group. Characteristics such as age, sex, smoking status, and social deprivation were also accounted for in the analyses.

Out of 9 million people; at the end of the study period, 23.3% of the healthy weight group, 32.6% of the underweight group, 16.8% of the overweight group and 14.2% of the group with obesity had had no doses of any COVID-19 vaccine.

In comparison, people in the healthy and high BMI groups who were vaccinated were around 70% less likely to be hospitalised than unvaccinated people. People with a healthy or a higher BMI were also around two-thirds less likely to die than their unvaccinated counterparts two weeks after a second dose.

The authors ended that the cause of the increased risk among people with obesity is unknown. It is consistent with the higher rate of seasonal 'flu infections in people with a higher BMI. They speculate that their findings may be explained, in part, by an altered immune response in heavier weight individuals. The reduced effectiveness of COVID-19 vaccines among people with a low BMI may also reflect a reduced immune response as a consequence of frailty or other conditions associated with low body weight.

Reference:

THE LANCET DIABETES & ENDO.: COVID-19 vaccine protects people of all body weights from hospitalization and death, study of 9 million adults in England suggests; THE LANCET https://www.thelancet.com/journals/landia/article/PIIS2213-8587(22)00158-9/fulltext.