Half of the antibodies generated by the tetanus vaccine may last up to 14 years, which is longer than previously thought, van Oers says. (This is known as the half-life.)
But some people produce fewer antibodies than others, he notes.
Antibodies don't tell the full story either, he explains.
"Your body will also remember tetanus, even if you are low on antibodies," he says. "Your body will immediately see it as foreign, and then your B-cells, which are antibody-manufacturing cells, will crank out antibodies as soon as the threat comes on."