Scientists have warned that the coronavirus vaccine manufactured by Pfizer may be less effective in people who are obese.
Researchers in Italy have said obese people 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.