Journal of Infectious Diseases Advance Access published August 4, 2015
BRIEF REPORT
The Decline of Pertussis-Specific Antibodies After Tetanus, Diphtheria, and Acellular Pertussis Immunization in Late Pregnancy Bahaa Abu Raya,1,4,a Isaac Srugo,1,2,4,a Aharon Kessel,3,4 Michael Peterman,2 Avraham Vaknin,4 and Ellen Bamberger2,4 1
We prospectively measured pertussis-specific antibodies 9– 15 months after delivery in women immunized with tetanus, diphtheria, and acellular pertussis (Tdap) after the 20th week of their recent pregnancy. The Tdap-immunized women (n = 38) exhibited a decline in geometric mean concentrations between their peripartum and follow-up levels for immunoglobulin G to pertussis toxin (21.48 [95% confidence interval, 12.51–36.89] vs 11.72 [7.09–19.37] IU/mL];); filamentous hemagglutinin (185.95 [157.93–218.94] vs 140.33 IU/mL [113.46–173.57] IU/mL); and pertactin (171.52 [120.73– 243.67] vs 83.74 [60.58–115.75] IU/mL) (all P < .001). For women immunized with Tdap during late pregnancy, pertussis-specific immunoglobulin G levels decreased significantly 9–15 months after delivery. Keywords. maternal immunization; tetanus-diphtheriaacellular pertussis; pertussis; immunoglobulin G; pertussis toxin.
The significant resurgence of pertussis over the last decade has prompted public health policy makers to introduce strategies by which to lessen its high morbidity and mortality rates, particularly among young infants [1]. The Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention now recommends the immunization of all pregnant women with tetanus, diphtheria, and acellular pertussis (Tdap), irrespective of their immunization status, preferably at 27–36 weeks in
Received 18 April 2015; accepted 30 May 2015. a B. A. and I. S. contributed equally to this work. Correspondence: Bahaa Abu Raya, MD, Department of Pediatrics, Bnai Zion Medical Center, Golomb St 47, Haifa 31048, Israel ([email protected]). The Journal of Infectious Diseases® © The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@ oup.com. DOI: 10.1093/infdis/jiv324
METHODS Study Design
This prospective study, conducted in January and February 2015 in northern Israel, comprised the sequential sampling, 9–15 months after delivery, of women who delivered between November 2013 and May 2014 and who took part in our earlier study that examined the preferential time period to immunize pregnant women with Tdap [8]. The inclusion criteria for the initial cohort were women with singleton births at gestational age ≥36 weeks who had received Tdap after the 20th week of the recent pregnancy [8]. Periparturient women unimmunized for pertussis during the recent pregnancy were the control group. Women were excluded from the initial recruitment if they had ≥1 of the following: an underlying immunological disease, receipt of immunoglobulins or immunosuppressive drugs in the previous year, receipt of blood products 3 months before delivery, documented pertussis infection (culture, polymerase chain reaction, or IgG to pertussis toxin [PT] ≥94 IU/mL) [10] or suspected pertussis infection (cough lasting >2 weeks) within the previous 5 years, receipt of a vaccine containing pertussis antigens within 5 years of the current pregnancy, receipt of any vaccine besides BRIEF REPORT
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Department of Pediatrics, 2Clinical Microbiology Laboratory, 3Division of Allergy and Clinical Immunology, Bnai Zion Medical Center, and 4The Ruth and Bruce Rappaport Faculty of Medicine, Technion–Israel Institute of Technology, Haifa
each pregnancy, regardless of the interval between pregnancies [2].Israel’s Ministry of Health adopted this immunization strategy in 2013. This public health measure is aimed at protecting vulnerable infants by reducing maternal risk of contracting pertussis and transmitting it to young infants, enhancing the transplacental transfer of pertussis immunoglobulin (Ig) G and the induction of breast milk pertussis-specific antibodies [3, 4]. Pertussis immunization induces pertussis-specific antibodies in the recipient, but their differential decay is affected by host factors [5, 6]. Halperin et al [7] examined women of childbearing age and postpartum women for 1 month after acellular pertussis vaccination and found that the antibody response was rapid and approached peak levels by day 14. However, studies involving Tdap immunization of pregnant women merit particular consideration, because pregnancy is a unique host state host and continues to be an area of considerable controversy. Although Tdap immunization during pregnancy induces high pertussis-specific antibody levels in the peripartum period and up to 2 months after delivery, the persistence of pertussis antibodies in maternal serum samples beyond 2 months is unknown [8, 9]. Accordingly, the aim of the current study was to evaluate the kinetics of pertussis-specific antibodies after Tdap immunization during late pregnancy.
Tdap within 2 weeks of delivery, and, finally, delivery of a newborn with a birth weight 2 weeks) after the recent delivery, or receipt of a pertussis-containing vaccine after the recent delivery. The study was approved by the medical center’s internal review board, and all participating women gave informed consent. Study Vaccine
The demographic and clinical characteristics of the Tdapimmunized women were compared with those of the women who did not receive Tdap during the recent pregnancy via a 2-sample t test for continuous data and χ2 or Fisher exact test, where appropriate, for categorical data. Antibody levels below the limit of detection were assigned the lower limit of detection value for that antigen. Geometric mean concentration (GMC) and 95% confidence intervals (CIs) were calculated for antigens in the peripartum period and at follow-up. Independent sample Mann–Whitney U tests were used to test for differences in antibody levels between the Tdap-immunized and unimmunized women. The Wilcoxon signed rank test (1 tailed) was used to test for a statistically significant decline in antibody levels from peripartum to follow-up. Data were analyzed using SPSS software, version 21.0. Differences were considered statistically significant at P < .05.
Study Procedure
All women recruited into the initial cohort who agreed to participate in the follow-up study were enrolled. The women were questioned as to whether they or their infants had suspected clinical pertussis (cough lasting >2 weeks) and/or laboratoryconfirmed pertussis. The women were also questioned about possible exposure to suspected clinical and or laboratoryconfirmed pertussis since delivery. A venous blood sample was then obtained by the investigators, transferred to Bnai Zion Medical Laboratory, Haifa, Israel, and stored up to 1 night at a temperature of 2°C until processing. Venous Blood Processing
Blood samples were centrifuged at 3500g for 10 minutes at Bnai Zion Medical Center’s Clinical Microbiology laboratory and stored at −20°C in a frost-free freezer before the analysis of pertussis-specific antibodies. Antibody Assay
Pertussis-specific IgG and IgA were measured by a validated IgG- and IgA-specific enzyme-linked immunosorbent assay in maternal serum samples (EUROIMMUN Medizinische Labordiagnostika). Results were reported in international units per milliliter, according to the European Union Perstrain group recommendations [11]. The anti–Bordetella pertussis controls of the anti–Bordetella PT enzyme-linked immunosorbent assay were calibrated using the first International World Health Organization standard (WHO International Standard Pertussis Antiserum, human, first International Standard National Institute for Biological Standards and Control [NIBSC] code 06/140). The lower limits of detection for IgG and IgA to PT were 0.2 and 0.7 IU/mL, respectively; the lower limits for IgG and IgA to FHA were 1 and 0.2 IU/mL, respectively; and the lower limit for IgG to pertactin was 0.6 IU/mL. 2
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BRIEF REPORT
RESULTS Thirty-nine Tdap-immunized and 11 unimmunized women agreed to participate. Two women were excluded from further analysis: a Tdap-immunized woman and a woman who was unimmunized during the recent pregnancy reported cough lasting >2 weeks, although neither underwent pertussis laboratory testing (Supplementary Figure 1). The final cohort comprised 38 Tdap-immunized (mean age, 32.6 years; range, 20–47 years) and 10 unimmunized women (mean age, 31.9 years; range, 26–40 years) who were followed up for a mean of 378 (range, 268–471) and 415 (397–431) days after delivery, respectively. Tdap-immunized women were immunized between 23.1 and 37.4 gestational weeks (mean, 50.6 days before delivery; range, 6–115 days). The demographic and clinical characteristics of the study population are presented in Supplementary Table 1. There were no statistically significant differences between the Tdapimmunized and unimmunized women and their newborns in maternal and pregnancy morbidity, gestational age, and mean time between delivery and follow-up (Supplementary Table 1).
Pertussis Exposure History
Aiming to exclude women who may have experienced natural pertussis antibody boosting, we questioned all participants about known potential exposure(s) to any suspected or laboratory-confirmed case of clinical pertussis. There were no significant differences in history of pertussis exposure or infection between the Tdap-immunized and unimmunized women, with exception that 2 of the unimmunized but none of the immunized women reported suspected pertussis >5 years before the most recent pregnancy (Supplementary Table 1).
Downloaded from http://jid.oxfordjournals.org/ at University of Georgia on August 5, 2015
All participants were immunized during their most recent pregnancy with Tdap (Boostrix) containing ≥20 IU of tetanus toxoid, ≥20 IU of diphtheria toxoid, 8 µg of PT, 8 µg of filamentous hemagglutinin (FHA), and 2.5 µg of pertactin.
Statistical Analysis
12.51–36.89) versus 0.77 (95% CI, .18–3.38) IU/mL, respectively (P < .001). At follow-up, the Tdap-immunized women maintained significantly higher GMCs than unimmunized women, 11.72 (95% CI, 7.09–19.37) versus 1.41 (95% CI, .32–6.14) IU/mL, respectively (P = .007). Only the Tdapimmunized women exhibited a significant decline in GMCs of IgG to PT between the initial levels and the follow-up period (P < .001) (Figure 2A). IgG to FHA
IgG to Pertactin
At delivery, Tdap-immunized women had higher GMCs of IgG to pertactin than unimmunized women, 171.52 (95% CI, 120.73– 243.67) versus 7.77 (95% CI, 1.94–31.07) IU/mL, respectively (P < .001). At follow-up, the Tdap-immunized women maintained significantly higher antibody levels than the unimmunized women, 83.74 (95% CI, 60.58–115.75) versus 5.98 (95% CI, 1.56– 22.97) IU/mL, respectively (P < .001). Only the Tdap-immunized women exhibited a significant decline in GMCs of IgG to pertactin between the initial levels and the follow-up period (P < .001) (Figure 2C). IgA to PT
Figure 1. A–C, Scatter graph of maternal serum immunoglobulin (Ig) G to pertussis toxin (PT), filamentous hemagglutinin (FHA), and pertactin (PRN) concentrations at peripartum and 9–15 months after delivery in women immunized with tetanus, diphtheria, and acellular pertussis (Tdap) and unimmunized women during their most recent pregnancy.
At delivery, Tdap-immunized women had higher GMCs of IgA to PT than unimmunized women, 3.22 (95% CI, 2.39–4.34) versus 1.24 (95% CI, .63–2.47) IU/mL, respectively (P = .002). At follow-up, the Tdap-immunized women maintained significantly higher GMCs than the unimmunized women, 2.61 (95% CI, 1.92–3.54) versus 0.82 (95% CI, .64–1.06) IU/mL, respectively (P = .001). Neither the Tdap-immunized women nor the unimmunized women had a significant decline in GMCs of IgA to PT between initial levels and the follow-up period (P = .10 and P = .25, respectively).
Pertussis-Specific Antibody Kinetics
The levels of pertussis-specific antibodies in maternal serum samples of Tdap-immunized and unimmunized participants were compared twice: during the peripartum period and after follow-up of 9–15 months after delivery (Figure 1). IgG to PT
At delivery, Tdap-immunized women had higher GMCs of IgG to PT than unimmunized women, 21.48 (95% CI,
IgA to FHA
At delivery, Tdap-immunized women had higher GMCs of IgA to PT than unimmunized women, 30.16 (95% CI, 20.41–44.58) versus 2.42 (95% CI, 1.12–5.20) IU/mL, respectively (P < .001). At follow-up, the Tdap-immunized women maintained significantly higher GMCs than the unimmunized women, 34.24 (95% CI, 25.03–46.85) versus 5.34 (95% CI, 3.56–8.02) IU/ mL, respectively (P = .001). At follow-up, there was no BRIEF REPORT
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At delivery, Tdap-immunized women had higher GMCs of IgG to FHA than unimmunized women, 185.95 (95% CI, 157.93– 218.94) versus 12.02 (95% CI, 7.82–18.47) IU/mL, respectively (P < .001). At follow-up, the Tdap- immunized women maintained significantly higher antibody levels than the unimmunized women, 140.33 (95% CI, 113.46–173.57) versus 17.01 (95% CI, 9.31–31.05)IU/mL, respectively (P = .007). Only the Tdap-immunized women exhibited a significant decline in GMCs of IgG to FHA between the initial levels and the follow-up period (P = .001) (Figure 2B).
DISCUSSION
significant decline in either the Tdap-immunized or the unimmunized women, but instead a significant increase in GMCs of IgA to FHA between the initial levels and the follow-up period for both groups (P = .02). 4
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BRIEF REPORT
Supplementary Data Supplementary materials are available at The Journal of Infectious Diseases online (http://jid.oxfordjournals.org). Supplementary materials consist of data provided by the author that are published to benefit the reader. The posted materials are not copyedited. The contents of all supplementary data are the sole responsibility of the authors. Questions or messages regarding errors should be addressed to the author.
Notes Potential conflicts of interest. interest.
All authors: No potential conflicts of
Downloaded from http://jid.oxfordjournals.org/ at University of Georgia on August 5, 2015
Figure 2. A–C, Geometric mean concentrations (GMCs) of maternal serum immunoglobulin (Ig) G to pertussis toxin (PT), filamentous hemagglutinin (FHA), and pertactin (PRN) during the peripartum period and 9–15 months after delivery in women immunized with tetanus, diphtheria, and acellular pertussis (Tdap) and unimmunized women during their most recent pregnancy. The GMCs of Tdap-immunized and unimmunized women were compared using independent sample Mann–Whitney U tests, and Wilcoxon signed rank tests (1 tailed) were used to determine whether there was a statistically significant decline in GMCs between the peripartum period and the follow-up.
Despite various attempts to reduce pertussis disease among young infants, the associated morbidity and mortality continues to be worrisome, with US data from 2014 including 28 660 pertussis cases and 9 deaths; among those who died, 7 were aged
BRIEF REPORT
The Decline of Pertussis-Specific Antibodies After Tetanus, Diphtheria, and Acellular Pertussis Immunization in Late Pregnancy Bahaa Abu Raya,1,4,a Isaac Srugo,1,2,4,a Aharon Kessel,3,4 Michael Peterman,2 Avraham Vaknin,4 and Ellen Bamberger2,4 1
We prospectively measured pertussis-specific antibodies 9– 15 months after delivery in women immunized with tetanus, diphtheria, and acellular pertussis (Tdap) after the 20th week of their recent pregnancy. The Tdap-immunized women (n = 38) exhibited a decline in geometric mean concentrations between their peripartum and follow-up levels for immunoglobulin G to pertussis toxin (21.48 [95% confidence interval, 12.51–36.89] vs 11.72 [7.09–19.37] IU/mL];); filamentous hemagglutinin (185.95 [157.93–218.94] vs 140.33 IU/mL [113.46–173.57] IU/mL); and pertactin (171.52 [120.73– 243.67] vs 83.74 [60.58–115.75] IU/mL) (all P < .001). For women immunized with Tdap during late pregnancy, pertussis-specific immunoglobulin G levels decreased significantly 9–15 months after delivery. Keywords. maternal immunization; tetanus-diphtheriaacellular pertussis; pertussis; immunoglobulin G; pertussis toxin.
The significant resurgence of pertussis over the last decade has prompted public health policy makers to introduce strategies by which to lessen its high morbidity and mortality rates, particularly among young infants [1]. The Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention now recommends the immunization of all pregnant women with tetanus, diphtheria, and acellular pertussis (Tdap), irrespective of their immunization status, preferably at 27–36 weeks in
Received 18 April 2015; accepted 30 May 2015. a B. A. and I. S. contributed equally to this work. Correspondence: Bahaa Abu Raya, MD, Department of Pediatrics, Bnai Zion Medical Center, Golomb St 47, Haifa 31048, Israel ([email protected]). The Journal of Infectious Diseases® © The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@ oup.com. DOI: 10.1093/infdis/jiv324
METHODS Study Design
This prospective study, conducted in January and February 2015 in northern Israel, comprised the sequential sampling, 9–15 months after delivery, of women who delivered between November 2013 and May 2014 and who took part in our earlier study that examined the preferential time period to immunize pregnant women with Tdap [8]. The inclusion criteria for the initial cohort were women with singleton births at gestational age ≥36 weeks who had received Tdap after the 20th week of the recent pregnancy [8]. Periparturient women unimmunized for pertussis during the recent pregnancy were the control group. Women were excluded from the initial recruitment if they had ≥1 of the following: an underlying immunological disease, receipt of immunoglobulins or immunosuppressive drugs in the previous year, receipt of blood products 3 months before delivery, documented pertussis infection (culture, polymerase chain reaction, or IgG to pertussis toxin [PT] ≥94 IU/mL) [10] or suspected pertussis infection (cough lasting >2 weeks) within the previous 5 years, receipt of a vaccine containing pertussis antigens within 5 years of the current pregnancy, receipt of any vaccine besides BRIEF REPORT
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Downloaded from http://jid.oxfordjournals.org/ at University of Georgia on August 5, 2015
Department of Pediatrics, 2Clinical Microbiology Laboratory, 3Division of Allergy and Clinical Immunology, Bnai Zion Medical Center, and 4The Ruth and Bruce Rappaport Faculty of Medicine, Technion–Israel Institute of Technology, Haifa
each pregnancy, regardless of the interval between pregnancies [2].Israel’s Ministry of Health adopted this immunization strategy in 2013. This public health measure is aimed at protecting vulnerable infants by reducing maternal risk of contracting pertussis and transmitting it to young infants, enhancing the transplacental transfer of pertussis immunoglobulin (Ig) G and the induction of breast milk pertussis-specific antibodies [3, 4]. Pertussis immunization induces pertussis-specific antibodies in the recipient, but their differential decay is affected by host factors [5, 6]. Halperin et al [7] examined women of childbearing age and postpartum women for 1 month after acellular pertussis vaccination and found that the antibody response was rapid and approached peak levels by day 14. However, studies involving Tdap immunization of pregnant women merit particular consideration, because pregnancy is a unique host state host and continues to be an area of considerable controversy. Although Tdap immunization during pregnancy induces high pertussis-specific antibody levels in the peripartum period and up to 2 months after delivery, the persistence of pertussis antibodies in maternal serum samples beyond 2 months is unknown [8, 9]. Accordingly, the aim of the current study was to evaluate the kinetics of pertussis-specific antibodies after Tdap immunization during late pregnancy.
Tdap within 2 weeks of delivery, and, finally, delivery of a newborn with a birth weight 2 weeks) after the recent delivery, or receipt of a pertussis-containing vaccine after the recent delivery. The study was approved by the medical center’s internal review board, and all participating women gave informed consent. Study Vaccine
The demographic and clinical characteristics of the Tdapimmunized women were compared with those of the women who did not receive Tdap during the recent pregnancy via a 2-sample t test for continuous data and χ2 or Fisher exact test, where appropriate, for categorical data. Antibody levels below the limit of detection were assigned the lower limit of detection value for that antigen. Geometric mean concentration (GMC) and 95% confidence intervals (CIs) were calculated for antigens in the peripartum period and at follow-up. Independent sample Mann–Whitney U tests were used to test for differences in antibody levels between the Tdap-immunized and unimmunized women. The Wilcoxon signed rank test (1 tailed) was used to test for a statistically significant decline in antibody levels from peripartum to follow-up. Data were analyzed using SPSS software, version 21.0. Differences were considered statistically significant at P < .05.
Study Procedure
All women recruited into the initial cohort who agreed to participate in the follow-up study were enrolled. The women were questioned as to whether they or their infants had suspected clinical pertussis (cough lasting >2 weeks) and/or laboratoryconfirmed pertussis. The women were also questioned about possible exposure to suspected clinical and or laboratoryconfirmed pertussis since delivery. A venous blood sample was then obtained by the investigators, transferred to Bnai Zion Medical Laboratory, Haifa, Israel, and stored up to 1 night at a temperature of 2°C until processing. Venous Blood Processing
Blood samples were centrifuged at 3500g for 10 minutes at Bnai Zion Medical Center’s Clinical Microbiology laboratory and stored at −20°C in a frost-free freezer before the analysis of pertussis-specific antibodies. Antibody Assay
Pertussis-specific IgG and IgA were measured by a validated IgG- and IgA-specific enzyme-linked immunosorbent assay in maternal serum samples (EUROIMMUN Medizinische Labordiagnostika). Results were reported in international units per milliliter, according to the European Union Perstrain group recommendations [11]. The anti–Bordetella pertussis controls of the anti–Bordetella PT enzyme-linked immunosorbent assay were calibrated using the first International World Health Organization standard (WHO International Standard Pertussis Antiserum, human, first International Standard National Institute for Biological Standards and Control [NIBSC] code 06/140). The lower limits of detection for IgG and IgA to PT were 0.2 and 0.7 IU/mL, respectively; the lower limits for IgG and IgA to FHA were 1 and 0.2 IU/mL, respectively; and the lower limit for IgG to pertactin was 0.6 IU/mL. 2
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RESULTS Thirty-nine Tdap-immunized and 11 unimmunized women agreed to participate. Two women were excluded from further analysis: a Tdap-immunized woman and a woman who was unimmunized during the recent pregnancy reported cough lasting >2 weeks, although neither underwent pertussis laboratory testing (Supplementary Figure 1). The final cohort comprised 38 Tdap-immunized (mean age, 32.6 years; range, 20–47 years) and 10 unimmunized women (mean age, 31.9 years; range, 26–40 years) who were followed up for a mean of 378 (range, 268–471) and 415 (397–431) days after delivery, respectively. Tdap-immunized women were immunized between 23.1 and 37.4 gestational weeks (mean, 50.6 days before delivery; range, 6–115 days). The demographic and clinical characteristics of the study population are presented in Supplementary Table 1. There were no statistically significant differences between the Tdapimmunized and unimmunized women and their newborns in maternal and pregnancy morbidity, gestational age, and mean time between delivery and follow-up (Supplementary Table 1).
Pertussis Exposure History
Aiming to exclude women who may have experienced natural pertussis antibody boosting, we questioned all participants about known potential exposure(s) to any suspected or laboratory-confirmed case of clinical pertussis. There were no significant differences in history of pertussis exposure or infection between the Tdap-immunized and unimmunized women, with exception that 2 of the unimmunized but none of the immunized women reported suspected pertussis >5 years before the most recent pregnancy (Supplementary Table 1).
Downloaded from http://jid.oxfordjournals.org/ at University of Georgia on August 5, 2015
All participants were immunized during their most recent pregnancy with Tdap (Boostrix) containing ≥20 IU of tetanus toxoid, ≥20 IU of diphtheria toxoid, 8 µg of PT, 8 µg of filamentous hemagglutinin (FHA), and 2.5 µg of pertactin.
Statistical Analysis
12.51–36.89) versus 0.77 (95% CI, .18–3.38) IU/mL, respectively (P < .001). At follow-up, the Tdap-immunized women maintained significantly higher GMCs than unimmunized women, 11.72 (95% CI, 7.09–19.37) versus 1.41 (95% CI, .32–6.14) IU/mL, respectively (P = .007). Only the Tdapimmunized women exhibited a significant decline in GMCs of IgG to PT between the initial levels and the follow-up period (P < .001) (Figure 2A). IgG to FHA
IgG to Pertactin
At delivery, Tdap-immunized women had higher GMCs of IgG to pertactin than unimmunized women, 171.52 (95% CI, 120.73– 243.67) versus 7.77 (95% CI, 1.94–31.07) IU/mL, respectively (P < .001). At follow-up, the Tdap-immunized women maintained significantly higher antibody levels than the unimmunized women, 83.74 (95% CI, 60.58–115.75) versus 5.98 (95% CI, 1.56– 22.97) IU/mL, respectively (P < .001). Only the Tdap-immunized women exhibited a significant decline in GMCs of IgG to pertactin between the initial levels and the follow-up period (P < .001) (Figure 2C). IgA to PT
Figure 1. A–C, Scatter graph of maternal serum immunoglobulin (Ig) G to pertussis toxin (PT), filamentous hemagglutinin (FHA), and pertactin (PRN) concentrations at peripartum and 9–15 months after delivery in women immunized with tetanus, diphtheria, and acellular pertussis (Tdap) and unimmunized women during their most recent pregnancy.
At delivery, Tdap-immunized women had higher GMCs of IgA to PT than unimmunized women, 3.22 (95% CI, 2.39–4.34) versus 1.24 (95% CI, .63–2.47) IU/mL, respectively (P = .002). At follow-up, the Tdap-immunized women maintained significantly higher GMCs than the unimmunized women, 2.61 (95% CI, 1.92–3.54) versus 0.82 (95% CI, .64–1.06) IU/mL, respectively (P = .001). Neither the Tdap-immunized women nor the unimmunized women had a significant decline in GMCs of IgA to PT between initial levels and the follow-up period (P = .10 and P = .25, respectively).
Pertussis-Specific Antibody Kinetics
The levels of pertussis-specific antibodies in maternal serum samples of Tdap-immunized and unimmunized participants were compared twice: during the peripartum period and after follow-up of 9–15 months after delivery (Figure 1). IgG to PT
At delivery, Tdap-immunized women had higher GMCs of IgG to PT than unimmunized women, 21.48 (95% CI,
IgA to FHA
At delivery, Tdap-immunized women had higher GMCs of IgA to PT than unimmunized women, 30.16 (95% CI, 20.41–44.58) versus 2.42 (95% CI, 1.12–5.20) IU/mL, respectively (P < .001). At follow-up, the Tdap-immunized women maintained significantly higher GMCs than the unimmunized women, 34.24 (95% CI, 25.03–46.85) versus 5.34 (95% CI, 3.56–8.02) IU/ mL, respectively (P = .001). At follow-up, there was no BRIEF REPORT
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At delivery, Tdap-immunized women had higher GMCs of IgG to FHA than unimmunized women, 185.95 (95% CI, 157.93– 218.94) versus 12.02 (95% CI, 7.82–18.47) IU/mL, respectively (P < .001). At follow-up, the Tdap- immunized women maintained significantly higher antibody levels than the unimmunized women, 140.33 (95% CI, 113.46–173.57) versus 17.01 (95% CI, 9.31–31.05)IU/mL, respectively (P = .007). Only the Tdap-immunized women exhibited a significant decline in GMCs of IgG to FHA between the initial levels and the follow-up period (P = .001) (Figure 2B).
DISCUSSION
significant decline in either the Tdap-immunized or the unimmunized women, but instead a significant increase in GMCs of IgA to FHA between the initial levels and the follow-up period for both groups (P = .02). 4
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Supplementary Data Supplementary materials are available at The Journal of Infectious Diseases online (http://jid.oxfordjournals.org). Supplementary materials consist of data provided by the author that are published to benefit the reader. The posted materials are not copyedited. The contents of all supplementary data are the sole responsibility of the authors. Questions or messages regarding errors should be addressed to the author.
Notes Potential conflicts of interest. interest.
All authors: No potential conflicts of
Downloaded from http://jid.oxfordjournals.org/ at University of Georgia on August 5, 2015
Figure 2. A–C, Geometric mean concentrations (GMCs) of maternal serum immunoglobulin (Ig) G to pertussis toxin (PT), filamentous hemagglutinin (FHA), and pertactin (PRN) during the peripartum period and 9–15 months after delivery in women immunized with tetanus, diphtheria, and acellular pertussis (Tdap) and unimmunized women during their most recent pregnancy. The GMCs of Tdap-immunized and unimmunized women were compared using independent sample Mann–Whitney U tests, and Wilcoxon signed rank tests (1 tailed) were used to determine whether there was a statistically significant decline in GMCs between the peripartum period and the follow-up.
Despite various attempts to reduce pertussis disease among young infants, the associated morbidity and mortality continues to be worrisome, with US data from 2014 including 28 660 pertussis cases and 9 deaths; among those who died, 7 were aged
