New study: COVID-19 vaccine protection wanes faster in the severely obese

Monday 15 May 2023

A study co-authored by School of Medicine staff has found that protection provided by COVID-19 vaccination declines more rapidly in people with severe obesity. Led by the Universities of Edinburgh and Cambridge, the work involved analysing data on severe COVID-19 outcomes and COVID-19 antibody functioning in fully vaccinated adults. Population and Behavioural Science Research Division Head Professor Colin McCowan and Honorary Research Fellow Dr Utkarsh Agrawal contributed to the study through their work on the EAVE II project. Based at the University of Edinburgh, EAVE II tracked the spread of COVID-19 in Scotland and monitored vaccine effectiveness.

Drawing on data from 3.6 million members of the Scottish population, the EAVE II team examined rates of hospitalisation and mortality due to COVID-19 among fully vaccinated adults. ‘Fully vaccinated’ was defined as having received two doses of the Pfizer-BioNTech BNT162b2 mRNA or AstraZeneca ChAdOx1 vaccines. The researchers found that people with severe obesity (Body Mass Index (BMI) of greater than 40 kg/m2) had a 76% higher risk of severe COVID-19 outcomes than those with a normal BMI (18.5–24.9 kg/m2). Moreover, as Professor McCowan explained, ‘these events happened more quickly after vaccination.’ In those with severe obesity, such complications typically arose within 10 or more weeks, as compared to 20 or more weeks for those of normal weight.

In parallel, the Cambridge team analysed the COVID-19 immune response of fully vaccinated adults with severe obesity attending Addenbrooke’s Hospital. They compared the number and functioning of COVID-19 antibodies in this sample to those of people of normal weight. They then assessed the same measures after both groups had received a third ‘booster’ vaccine dose.

Six months after participants received their second dose, although the groups had similar antibody levels, the cells’ ability to fight the virus was reduced in those with severe obesity. This ‘neutralising capacity’ was undetectable in 55% of such individuals, as compared to only 12% of people with a normal BMI. Although this capacity was restored after participants received their third dose, testing at the 15-week mark revealed that it waned significantly faster in those with severe obesity.

‘This work suggests that whilst vaccines do offer additional protection for people with obesity, the strength of effect and how long it lasts are not as good as for people of normal weight,’ said Professor McCowan. This indicates that this population will likely require more frequent vaccine ‘boosters,’ which could have significant implications for future vaccine prioritisation policies.

The full article, published in Nature Medicine, is available to read here.

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