One year immunogenicity and safety of subunit plague vaccine in Chinese healthy adults: An extended open-label study

Abstract

Background: To evaluate the one-year immunogenicity and safety of a subunit plague vaccine.

Methods: In the initial study, 240 healthy adults aged 18-55 years were administrated with 2 doses of 15 or 30 µg plague vaccines at day 0 and 28, respectively. In this extended follow-up study, we evaluated the immunogenicity and safety of the plague vaccine up to one year.

Results: For antibody to envelope antigen faction 1 (F1) antigen, titers were up to new peaks at month 6, then declined slowly to month 12, but remained at higher levels than those at day 56. Geometric mean titers (GMTs) of F1 were significantly higher in 30 µg group than those in 15 µg group at month 6 and 12 (P < 0.0001 and P < 0.001). However, approximate 100% seroconversion rates of F1 antibodies were found in both 15 and 30 µg groups at the both time points. For antibody to recombinant virulence (rV) antigen, titers and seroconversion rates were decreased sharply at month 6 and continue to decrease at month 12. GMTs and seroconversion rates were not significantly different between the 15 and 30 µg groups, respectively. No serious adverse events (SAEs) related to vaccine occurred.

Conclusion: The new plague vaccine (F1+rV) induced a robust immune response up to 12 months and showed a good safety profile in adults aged 18-55 years.

Trial registration: ClinicalTrials.gov NCT02596308.

Keywords: immunogenicity; phase2a; plague vaccine; safety; vaccine clinical trial.

Figures

Figure 1.

Geometric mean titer of antibodies at various time points after the vaccination from day 0 through month 12. Error bars indicate 95% Confidence intervals (CI). The data of GMTs from day 0 to 56 have been showed in the initial study.20

Figure 2.

Accumulation curve of antibodies after vaccination at month 6 and 12. Figure A: Accumulation curve of antibodies to anti-F1 after vaccination in 15 and 30 groups at month 6 and 12. Figure B: Accumulation curve of antibodies to anti-rV after vaccination in 15 and 30 groups at month 6 and 12.