Vaccines contain TLR ligands. Vaccines were added (10× diluted) to recombinant HEK293 cell lines, functionally expressing a given TLR protein and a reporter gene driven by an nuclear factor-κB–inducible promoter. TLR stimulation was measured as activation of the reporter gene. The negative control value for each clone is the background signal. Positive control ligands used are: PAM2 for the HEK293-hTLR2 cell line, LPS K12 for the HEK293-hTLR4 cell line, and Flagellin for the HEK293-hTLR5 cell line. Data are expressed as optical density (OD) values.