Data has suggested that the Pfizer/BioNTech vaccine may be less effective in people with obesity.
According to Italian scientists, the coronavirus vaccine manufactured by Pfizer may be less effective in plus-size people, therefore, they may need bigger doses, or another top-up jab, to protect them against the virus.
They claim this is because compared to healthy people severely overweight healthcare workers generated only half the antibodies to fend off COVID-19 after receiving two doses of the Pfizer jab.
Antibodies are virus-fighting proteins that can stop the coronavirus infection.
They are a major part of the immune system but there are other parts too.
This is a double blow to severely overweight people as they are already considered to be more at risk of becoming critically ill or dying if they contract the virus.
Scientists say this could be down to obese people being more likely to have health conditions such as diabetes and high blood pressure which makes them more vulnerable.
Obesity is defined as having a BMI above 30.
Experts said it was also well known that it hampers the effectiveness of jabs as previous research has suggested the flu vaccine could be half as effective in severely overweight people.
But the study by Italian scientists is believed to be the first time the same link has been found for the coronavirus vaccine.
It has been published as a pre-print on medRxiv, and its methodology and findings have yet to be peer-reviewed by fellow scientists.