Immunization of pregnant women against pertussis: the effect of timing on antibody avidity.
BACKGROUND
The Centers for Disease Control and Prevention recommend tetanus-diphteria-acellular pertussis (Tdap) immunization during pregnancy, preferably at 27-36 weeks gestation.


OBJECTIVE
First, to assess the relative avidity index (RAI) of umbilical cord immunoglobulin G (IgG) to pertussis toxin (PT) for newborns of women immunized with Tdap during late pregnancy as compared to unimmunized women. Second, to assess whether there is a preferential period of gestational Tdap immunization that provides the highest RAI of umbilical cord IgG to PT.


METHODS
RAI of IgG to PT was assessed via an adapted ELISA using NH4SCN as a dissociating agent.


RESULTS
We found that newborns of women immunized with Tdap during late pregnancy (n=52) had higher mean RAI of umbilical cord IgG to PT than those of unimmunized women (n=8), 73.77%±12.08 (95% CI, 70.41-77.13) vs. 50.23%±21.32 (95% CI, 32.41-68.06), p<0.001. Further, the RAI of umbilical cord IgG to PT was significantly higher in newborns of women immunized at 27-30(+6) weeks gestation (n=20) when compared with newborns of women immunized at 31-36 weeks (n=22) and >36 weeks (n=7), 79.53%±5.61 (95% CI, 76.91-82.16) vs. 71.56%±12.58 (95% CI, 65.98-77.14) vs. 63.93%±17.98 (95% CI, 47.31-80.56), p<0.03.


CONCLUSIONS
Gestational Tdap immunization between 27 and 30(+6) weeks resulted in the highest avidity of IgG to PT conveyed at delivery as compared with immunization beyond 31 weeks gestation. Future studies should be conducted to confirm our findings to optimize pertussis-controlling strategies.
Department of Pediatrics, Bnai Zion Medical Center, Golomb St. 47, Haifa 31048, Israel; The Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Efron St. 1, Haifa 31096, Israel. Electronic address: baha_aboraya@yahoo.com.
Bahaa
B
Abu Raya
The Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Efron St. 1, Haifa 31096, Israel; Clinical Microbiology Laboratory, Bnai Zion Medical Center, Golomb St. 47, Haifa 31048, Israel.
Ellen
E
Bamberger
The Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Efron St. 1, Haifa 31096, Israel; Division of Allergy and Clinical Immunology, Bnai Zion Medical Center, Golomb St. 47, Haifa 31048, Israel.
Meital
M
Almog
Division of Allergy and Clinical Immunology, Bnai Zion Medical Center, Golomb St. 47, Haifa 31048, Israel.
Regina
R
Peri
Department of Pediatrics, Bnai Zion Medical Center, Golomb St. 47, Haifa 31048, Israel; The Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Efron St. 1, Haifa 31096, Israel; Clinical Microbiology Laboratory, Bnai Zion Medical Center, Golomb St. 47, Haifa 31048, Israel.
Isaac
I
Srugo
The Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Efron St. 1, Haifa 31096, Israel; Division of Allergy and Clinical Immunology, Bnai Zion Medical Center, Golomb St. 47, Haifa 31048, Israel.
Aharon
A
Kessel
D000328:Adult; D000907:Antibodies, Bacterial / Q000276:immunology*; D000915:Antibody Affinity / Q000276:immunology*; D001886:Bordetella pertussis / Q000276:immunology*; D022681:Diphtheria-Tetanus-acellular Pertussis Vaccines / Q000276:immunology*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007114:Immunization; D007074:Immunoglobulin G / Q000276:immunology; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D009017:Morbidity; D011247:Pregnancy; D055815:Young Adult
D000907:Antibodies, Bacterial; D022681:Diphtheria-Tetanus-acellular Pertussis Vaccines; D007074:Immunoglobulin G
Immunoglobulin G; Pertussis; Pertussis toxin; Relative avidity index; Tetanus–diphtheria–acellular pertussis maternal immunization