Immunisation needles aren't a one-size-fits-all

The standard 25 millimetre needle may not successfully deposit vaccines in the upper arms of up to 45 percent of obese individuals.

But the Medical Research Institute has found arm circumference and BMI can help professionals choose the correct needle length.

Director Professor Richard Beasley says getting this right is crucial.

He says if the vaccine comes up short, it is more likely the person receiving the vaccine will have a greater local reaction.

Beasley says for vaccines like influenza, it's also less likely to be effective.