A novel human papillomavirus (HPV)-16/18 vaccine made by Escherichia coli has been proved to be safe and extremely effective, and it has recently been licenced in China. This study aims to analyse the influence of vaccination timing discrepancies on the particular antibody response and suggest improved use of this vaccine in the real world as a post-hoc analysis of the phase III trial. A total of 3689 healthy women between the ages of 18 and 45 were randomly randomised to receive the bivalent HPV-16/18 vaccine on a 0-, 1-, and 6-month regimen with a broad vaccination interval. The initial immunisation interval was separated into three groups: 28–40 days, 41–50 days, and 51–60 days.
The second vaccination interval was separated into three groups: 103–139 days, 140–160 days, and 161–198 days. For both HPV-16 and HPV-18, the reverse cumulative curves for IgG of the three groups with different first vaccination intervals or different second vaccination intervals at month 7 virtually overlapped. All subgroups had GMC ratios more than 0.83 when compared to the normal vaccination schedule subgroup, with lower limits of 95 percent CIs larger than 0.64. In conclusion, a modest difference in the timing of the second and third doses has only a modest, inconsequential effect on the immunological response caused by the Escherichia coli-produced HPV-16/18 vaccine.