Exemplified for pertussis, the most likely causal variant defined by the fine-mapping in our VaccGene cohort was a HLA-DRB3 amino acid residue, but, when combining our data with those of a related phenotype from a UK dataset, we found near-equivalent evidence that the signal was instead linked to a HLA-DRB1 variant that could equally alter peptide binding or gene expression. The gene discussed is HLA-DRB1; the disease is pertussis.