Accelerated waning of the humoral response to COVID-19 vaccines in obesity

The first SCORPIO study paper was published today in Nature Medicine. The SCORPIO team at the University of Cambridge, teamed up with a team led by Professor Sir Aziz Sheikh at the University of Edinburgh.

During the pandemic, people with obesity were more likely to be hospitalised, require ventilators and to die from COVID-19. In the SCORPIO study, we set out to investigate how far two of the most extensively used vaccines protect people with obesity compared to those with a normal weight, over time.

By looking at real-time data tracking the health of 3.5 million people in the Scottish population as part of the EAVE II study, the Edinburgh team found that people with severe obesity (a BMI greater than 40 kg/m²) had a 76% higher risk of severe COVID-19 outcomes, compared to those with a normal BMI. A modest increase in risk was also seen in people with obesity (30-39.9kg/m²), which affects a quarter of the UK population, and those who were underweight. ‘Break-through infections’ after the second vaccine dose also led to hospitalisation and death sooner (from 10 weeks) among people with severe obesity, and among people with obesity (after 15 weeks), than among individuals with normal weight (after 20 weeks).

The University of Cambridge team studied people with severe obesity attending Addenbrooke’s Hospital in Cambridge, and compared the number and function of immune cells in their blood to those of people of normal weight. We found that six months after a second vaccine dose, people with severe obesity had similar levels of antibodies to the COVID-19 virus as those with a normal weight, but the ability of those antibodies to work efficiently to fight against the virus (known as ‘neutralisation capacity’) was reduced. 55% of individuals with severe obesity were found to have unquantifiable or undetectable ‘neutralising capacity’ compared to 12% of people with normal BMI. When given a third (booster) dose of a COVID-19 vaccine, the ability of the antibodies to neutralise the virus was restored in both the normal weight and severely obese groups. But we found that immunity again declined more rapidly in people with severe obesity, putting them at greater risk of infection with time.

The findings have important implications for vaccine prioritisation policies around the world and people with obesity are likely to need more frequent booster doses to maintain their immunity.

We are immensely grateful to all the participants for their involvement in the SCORPIO study.

You can read the paper online here.