People with severe obesity may need more frequent booster vaccinations against COVID-19 than those of a healthy weight in order to maintain their immunity. This is the warning of experts from the Universities of Cambridge and Edinburgh, who found that the protection given by Covid jabs wanes faster with a higher body mass index (BMI). According to the most recent Health Survey for England, more than a quarter of English adults are classified as obese, with the World Health Organisation reporting that cases of obesity have nearly tripled since 1975.
Clinical trials have shown that vaccination against Covid is highly effective at reducing the severity of symptoms and the risk of both hospitalisation and death following infection — including for people with obesity.
However, during the pandemic, people with obesity were found to be more likely to be admitted to hospital, require the support of ventilators, and to die from the virus.
The findings build on the results of previous studies that suggest that people with obesity might develop lower levels of antibodies against SARS-CoV-2 — the virus that causes COVID-19 — following vaccination.
Alongside this, researchers have warned that people with obesity may remain at a higher risk of severe disease if they contract the virus than their counterparts with a lower BMI.
The exact reasons for these phenomena, however, had been unclear.
The new research comes in the form of two related studies, both of which received funding from the Medical Research Council.
At the University of Edinburgh, epidemiologist Professor Sir Aziz Sheikh and his colleagues analysed data that tracked the health of 3.5 million people in Scotland in real-time.
This study — dubbed EAVE II — found that people with severe obesity had a 76 percent higher risk of severe Covid outcomes as compared to those of a healthy BMI.
A “modest increase” in risk was also seen in people with obesity that was not classified as severe, as well as those who were underweight.
(Obesity is defined as having a BMI in the range from 30–39.9 kilograms per square metre [6.14–8.18 pounds per square foot], while severe obesity starts at a BMI of 40. People are underweight, meanwhile, if they have a BMI beneath 18.5.)
Prof. Sheikh said: “Our findings demonstrate that that protection gained through COVID-19 vaccination drops off faster for people with severe obesity than those with a normal body mass index.”
“Using large-scale data assets such as the EAVE II platform in Scotland have enabled us to generate important and timely insights that enable improvements to the delivery of COVID-19 vaccine schedules in a post-pandemic UK.”
The second study — dubbed Sars-CoV-2, ResPonse In Obesity, or “SCORPIO” for short — involved an analysis of patients who visited the Addenbrooke’s Hospital in Cambridge.
The researchers compared the number and the function of immune cells in the blood of patients with obesity with those of people with a healthy BMI.
Observations for study began six months after each subject had been given their second vaccine dose — and covered the period during which they received their third jab, in order to see how each recipient’s body responded to the booster injection.
The team found that, six months after their second dose of Covid vaccine, people with severe obesity had similar levels of antibodies against SARS-CoV-2 as those subjects with a healthy BMI.
However, the team found that, in people with obesity, the ability of those antibodies to work efficiently to fight the virus — what experts call the “neutralisation capacity” — is reduced in people with obesity.
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Immunologist Dr James Thaventhiran of the MRC Toxicology Unit in Cambridge is one of the leaders of the SCORPIO study.
He said: “It is promising to see that booster vaccines restore the effectiveness of antibodies for people with severe obesity.”
However, he continued, “it is concerning that their levels decrease more quickly, after just 15 weeks.
“This shows that the vaccines work as well as in people with obesity, but the protection doesn’t last as long.”
Paper co-author and metabolism expert Professor Sadaf Farooqi of the Wellcome–MRC Institute of Metabolic Science is the other leader of the SCORPIO study.
He said: “More frequent booster doses are likely to be needed to maintain protection against COVID-19 in people with obesity.
“Because of the high prevalence of obesity across the globe, this poses a major challenge for health services.”
The full findings of the study were published in the journal Nature Medicine.
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