Coronavirus vaccine may not be as effective in obese people because their immune systems are weaker, scientists warn
- Past research has found the flu vaccine does not work as well in obese people
- High levels of blood sugar, inflammation and insulin resistance impair immunity
- Scientists should consider this when trialling new vaccines, experts say
- Obesity also raises the risk of hospitalisation or death if someone catches Covid
A coronavirus vaccine might not work as well in overweight people because their immune systems are weaker, scientists warn.
Experts around the world are scrambling to develop a jab that could protect peoplee from Covid-19 and allow life to return to normal, with efforts on track for next year.
But now experts say that obese people – one in three adults in Britain and 40 per cent of Americans – may not feel the benefits as much as their thinner neighbours.
Obesity already puts people at greater risk from coronavirus, with the odds of hospitalisation doubled and the risk of death almost 50 per cent higher.
This means some of the people who most need protection from the virus may not get it as well as others.
The flu jab doesn’t work as well in fat people, researchers have found in the past, and they fear the same could be true of any eventual vaccine against Covid-19.
This is because high levels of sugar in the blood, poor insulin control and swelling in the blood vessels – all more common in obese people – can stop immune cells from functioning as well as they should.
Researchers said this didn’t mean the vaccine wouldn’t work at all but that scientists should be aware it could be less effective.
Researchers say high blood sugar levels, which are more common in very overweight people, interfere with the ability of immune cells to do their jobs (stock image)
The warning was given by researchers from the University of North Carolina at Chapel Hill in the US in a paper exploring the link from obesity to Covid-19 complications.
‘We are not saying that the vaccine will be ineffective in populations with obesity,’ said Professor Melinda Beck, an author of the study.
‘But rather that obesity should be considered as a modifying factor to be considered for vaccine testing.
‘Even a less protective vaccine will still offer some level of immunity.’
Professor Beck and her colleagues suggested that scientists trialling experimental vaccines should consider whether people in the trials are obese and whether this affects the jab’s effectiveness.
They said: ‘It is urgent that any vaccine trials and studies include BMI [body mass index] as a potential confounder for vaccine effectiveness and protection.’
There are dozens of vaccine attempts being developed around the world right now, with many already in human trials.
Some of the leading options have been developed by scientists in Britain, with one developed by Oxford University already sold hundreds of millions of times to international governments.
Professor Beck and her team explained that obesity, defined as when someone has a body mass index (BMI) higher than 30, makes the immune system weaker.
High blood sugar, inflammation and insulin resistance – which affects the ability the control blood sugar – all contribute to this.
In the study the team said obesity ‘has been shown to impair the development of immunological memory’.
They said that people with excess body fat had weaker immunity after a flu vaccine and were twice as likely to still get the flu or flu-like illness despite the jab.
Past research looking at antibodies – virus-fighting molecules made by the immune system – found that although they were similar 30 days after a flu jab, ‘wane significantly more in adults with obesity’ over the course of a year.
They also did not produce certain other types of immune cells, known as T cells, as effectively.
This impaired immune response could also be what makes obese people more likely to get severely ill or die if they catch Covid-19, the scientists added.
Their review found that people with a BMI over 30 were 113 per cent more likely to end up in hospital, 74 per cent more likely to need intensive care, and 48 per cent more likely to die than people of a healthy weight.
Professor Beck added: ‘Individuals with obesity are also more likely to experience physical ailments that make fighting this disease harder, such as sleep apnea, which increases pulmonary hypertension [high blood pressure in the lungs], or a body mass index that increases difficulties in a hospital setting with intubation.’
The study was published in the scientific journal Obesity Reviews.