Anthrax vaccine recipients lack antibody against the loop neutralizing determinant: A protective neutralizing epitope from Bacillus anthracis protective antigen.

•Anthrax vaccine recipients lack antibody against the LND.•AVA and LND-vaccines elicit non-overlapping protective Ab specificities for anthrax.•An epitope-focused LND vaccine would complement PA-based vaccines.•The elicitation of LND Ab requires vaccination with an epitope-focused vaccine.