Titres to anti-Ad5 neutralising antibodies increase and persist up to 6 months post-vaccination.
Participants were from the FAS for immunogenicity analysis population (Ad5-nCoV, n = 371; Placebo group, n = 124). Based on the GMTs of anti-Ad5 on Day 0, Day 28 and Month 6, the number of participants with low (≤1:200) or high (>1:200) anti-Ad5 titres those from either the Ad5-nCoV (left panels) or Placebo groups (right panels) is presented. Participants in each group were separated based upon their pre-existing anti-Ad5 neutralising antibodies as low (≤1:200; i.e., 1:5, 1:10, 1:20, 1:40, 1:80, 1:160) or high (>1:200; i.e., 1:320, 1:640, 1:1280). The threshold for low and high anti-Ad5 titres is indicated with the dashed vertical line.The effect of pre-existing immunity to anti-Ad5 neutralising antibodies on the immunological responses to the vaccine was studied. Participants with pre-existing anti-Ad5 antibodies that had received the Ad5-nCoV vaccine (n = 317) were separated into seven subgroups: six subgroups had low (≤1:200) Ad5 titres and one subgroup had high (>1:200) Ad5 titres and one subgroup had high (>1:200) Ad5 titre (