Obesity speeds loss of immunity–research
MBABANE - New research suggests that protection offered by COVID-19 vaccines wanes more quickly in people with severe obesity compared to those of normal weight.
The COVID vaccines were introduced over two years ago and proved to have efficacy in boosting immunity against the virus. It has now emerged that for some groups they don’t generate as strong an immune response. These groups include older adults and people with weakened immune systems, for example, due to cancer or other medical conditions.
Likewise, obesity and its association with several other conditions such as type two diabetes, high blood pressure and chronic kidney disease has been found to be leading to an increased risk of severe COVID-19.
The effect of obesity on COVID-19 vaccine effectiveness, however, has not been well understood. But a new study in nature medicine found that obesity was linked to faster loss of immunity from COVID-19 vaccines.
Worth noting, people with obesity have an impaired immune response to other vaccines including those for influenza, rabies and hepatitis. COVID-19 vaccines generate antibodies which recognise the spike protein, a protein on the surface of SARS-CoV-2 (the virus that causes COVID-19) that allows it to attach to and infect body cells. The vaccines also prime immune cells called T cells to protect against severe COVID-19 if people contract the virus.
Protections
Since immunity acquired after two doses wanes in the months afterwards, many countries have elected to administer booster vaccines to maintain immune protection, particularly in vulnerable groups. Several studies have suggested that following COVID-19 vaccination, antibody levels may be lower in people with obesity than in the general population.
In recent years, a team of researchers from the University of Cambridge and the University of Edinburgh was assembled to investigate the effect of obesity on vaccine effectiveness over time.
They found that people with severe obesity, defined as a body mass index (BMI) over 40, had a 76 per cent increased risk of hospitalisation and death from COVID-19 after vaccination compared to those with a BMI in the normal range. The risk was also moderately increased in people who were obese (a BMI between 30 and 40) and those who were underweight (a BMI lower than 18.5).
The risk of severe disease from breakthrough infections after the second vaccine also began to increase more quickly among people with severe obesity (from around ten weeks post-vaccination) and among people with obesity from around 15 weeks compared with people of a normal weight (from around 20 weeks.
Response
The team conducted experiments to characterise the immune response to a third dose, or booster, of mRNA COVID vaccines (those made by Pfizer and Moderna) in people with severe obesity.
They studied 28 people with severe obesity attending Addenbrooke’s Hospital in Cambridge, and measured antibody levels and function as well as the number of immune cells in their blood, post-vaccination. We compared the results to those from 41 people of a normal weight. Although antibody levels were similar in samples from all participants before booster vaccination, the ability of antibodies to work efficiently to fight the virus, known as ‘neutralisation capacity’, was reduced among people with severe obesity. In 55 per cent of people with severe obesity we either couldn’t detect or quantify neutralisation capacity, compared to 12 per cent of people with normal BMI.
This might mean COVID-19 vaccines induce lower quality antibodies in people with obesity. It’s possible the antibodies are not able to bind to the virus with the same strength as in people of normal weight. After a booster, antibody function in people with obesity was restored to the same level as those of normal weight. However, using detailed measurements of B cells, which are responsible for antibody production and immune memory, it was found that these immune cells developed differently in the first couple of weeks after vaccination in people with obesity.
By repeating measurements of immune responses over time, we could see antibody levels and function declined more rapidly after the third dose in people with severe obesity.
However, there were some limitations in both parts of the study. Nonetheless, immunity from COVID-19 vaccines doesn’t seem to be as robust or long-lasting in people with obesity. With severe obesity affecting three per cent of the UK population and nine per cent of the US population, these findings have important implications.
Target
The study also highlighted the need for more targeted interventions to protect people with obesity from severe COVID-19. “Evidence shows weight loss of at least five per cent can reduce the risk of type two diabetes and other metabolic complications of obesity. Interventions that can lead to a sustained reduction in weight such as lifestyle modification, weight loss drugs, and bariatric surgery could similarly improve COVID outcomes,” the study found. It was said that weight loss may, likewise, improve vaccine responses,
“But, we need more research to investigate. Worth noting, the Ministry of Health and its partners have been encouraging emaSwati to get vaccinated and also take their booster shots. The Director of Health Services, Dr Velephi Okello elaborated that Eswatini had incorporated COVID-19 vaccination into the national immunisation programme therefore people should take the vaccines. She noted that with the winter season it was crucial that people took the jab as well as boosters for those who are already vaccinated.