Using a standard 1in needle to immunise obese adolescents against the hepatitis B virus produced a much weaker effect than using a longer needle, a new study has found.
Over three years of study, researchers vaccinated 22 young women and two young men in the shoulder, randomly assigning them to be injected with either a 1in or a 1.5in needle.
Once injected, vaccines trigger production of small molecules called antibodies, which kick-start the immune system if the patient is ever attacked by the virus again.
During the study a different antibody count was noted in patients injected with the different needles. In patients injected with the shorter needle the number of antibodies was almost halved, with lower count generally meaning a less robust response.
Mayo Clinic in Rochester Department of Infectious Diseases’ Dr Gregory Poland said doctors have known that vaccines tend not to work as well in heavy people.
“Long needles turn out to be less painful and have fewer side effects,” Poland said.