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Obesity reduces vaccine efficacy and may affect Covid-19 vaccine success rates

Obesity reduces vaccine efficacy and may affect Covid-19 vaccine success rates

Being obese or overweight weakens the immune system and could possibly make Covid-19 vaccines less effective.

Doctors have known for many years that vaccines, such as the flu vaccine, perform poorly in obese individuals, giving rise to the speculation that a similar response will occur in overweight patients undergoing Covid-19 vaccine treatment.

Experts believe the reason overweight and obese people respond poorly to vaccines is because fat tissues are very active and have been shown to inhibit the body’s immune response to viruses. When immune responses in the overweight and obese are suppressed, these patients may end up needing different dosages of vaccine for it to be effective, with some products potentially not being effective at all.

The ability of fat tissues to inhibit the immune system may be why obese people are more severely affected by Covid-19. According to a study published in Obesity Reviews, obese individuals are more likely to contract Covid-19 than people of healthy weight and have worse outcomes including being more than twice as likely to need to be admitted to hospital; and once in hospital they have a 74% higher chance of admission to an intensive care unit, and a 48% higher risk of death (1).

Although this is a cause for concern, Covid-19 vaccine producers, including AstraZeneca and Novavax said they had no plans to investigate the issue, while Moderna and Pfizer did not respond to requests for comment, according to an article published in The New York Times (2).

While Johnson & Johnson is enrolling obese individuals for their vaccine trials, experts conclude that governments and individuals must also address the social underpinnings of obesity - such as access to healthy food and healthcare – to ensure that Covid-19 is properly contained long after vaccines are available to the public.

1) Popkin, B.M., Du, S., Green, W.D., et al. Individuals with obesity and COVID-19: A global perspective on the epidemiology and biological relationships. Obesity Reviews, 2020; 21(11): e131128. Accessible at: (Last accessed: 11 December 2020)

2) Katherine J. Wu, “Studies Begin to Untangle Obesity’s Role in Covid-19,” The New York Times, (2020). Accessible at: (Last accessed: 11 December 2020)