Discussion
PERTUSSIS
Our study focused on the induction by pertussis booster vaccines of anamnestic anti-PT response to obtain antibody levels sufficiently high to likely protect newborns against severe pertussis in the first months of life (data will be presented later in a separate publication). The antibody level of our study formulations has elicited similar or higher levels than the comparator in pregnant women at day 28 post-vaccination which was previously shown to protect infants in a study conducted by Amirthalingam et al (2014) Findings from this phase 2 trial indicate that recombinant genetically inactivated acellular pertussis vaccines may be suitable for use in immunizing pregnant women at a range of doses. Not only were they non-inferior in terms of immunogenicity to the chemically inactivated pertussis vaccine licensed for this use in the pooled population of pregnant women and women of childbearing age (In this study, we found that 57% of pregnant women were seronegative for PT-IgG antibody at baseline which is in line with another study conducted in Thai pregnant women For both seroresponse rates and GMC/GMT for PT antibody and PT neutralizing antibody, our study formulations have elicited similar or higher levels than the comparator. The higher levels were observed with Tdap2For FHA antibody, ap1One limitation of this study in pregnant women is the small sample size. However, pooling of this study with the study in women of childbearing age provided adequate power for a non-inferiority comparison. The pooling was considered appropriate given the similar study methods, populations, immunogenicity testing in the same laboratory with the same validated assay, and adjustment of responses based on baseline titer, cohort, and treatment. Another limitation of this study is the fact that the immune system in pregnant women behave differently compared to non-pregnant women. By pooling the data, the effect of pregnancy on immune response will be decreased.More information on pertussis immune response at birth and in infants will be needed before generalized conclusions ranking the responses to the different vaccine formulations can be drawn. Additional data from later stages/phases of the same study are forthcoming to assess the impact of the timing of maternal vaccination (second versus third trimester of pregnancy) on IgG placental transfer to the infant and to explore the impact of maternal antibodies on infant responses to primary immunizations, including to pneumococcal conjugate vaccine (PCV).More extensive studies with the selected study vaccines should be then considered in pregnant women in other populations, in diverse countries, ethnicities, and social contexts.