Immunogenicity of a two-component (PT&FHA) acellular pertussis vaccine in various combinations

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1 Human Vaccines ISSN: (Print) (Online) Journal homepage: Immunogenicity of a two-component (PT&FHA) acellular pertussis vaccine in various combinations Emmanuel Vidor & Stanley A. Plotkin To cite this article: Emmanuel Vidor & Stanley A. Plotkin (2008) Immunogenicity of a twocomponent (PT&FHA) acellular pertussis vaccine in various combinations, Human Vaccines, 4:5, , DOI: /hv To link to this article: Copyright 2008 Landes Bioscience Published online: 01 Sep Submit your article to this journal Article views: 305 Citing articles: 23 View citing articles Full Terms & Conditions of access and use can be found at

2 [Human Vaccines 4:5, ; September/October 2008]; 2008 Landes Bioscience Review Immunogenicity of a two-component (PT & FHA) acellular pertussis vaccine in various combinations Emmanuel Vidor 1 and Stanley A. Plotkin 2, * Sanofi Pasteur; Campus Mérieux; 1 Marcy l Etoile, France; 2 Doylestown, Pennsylvania USA Key words: acellular pertussis vaccine (two-components), immunogenicity, efficacy, effectiveness, review Immunogenicity data for the pertussis components of the French diphtheria-tetanus-two component acellular pertussis vaccine (DTaP 2Fr ) obtained after primary series of immunizations were compiled from 75 study groups comprising 36 clinical trials or vaccination programs conducted between 1987 and DTaP 2Fr vaccine was administered either as a standalone vaccine or as the backbone of several combination vaccines that included IPV, HepB and/or PRP-T antigens. Most of the variability in responses was associated with differences in the schedules, and to a lesser extent the geographical region where the study was performed, suggesting the importance of ethno-ecological factors. However the addition of other vaccine antigens did not affect the immunogenicity of the ap 2Fr antigens. The immune responses to the PT and FHA antigens of the DTaP 2Fr vaccine used in the Sénégal efficacy trial, which established its good efficacy relative to a highly effective DTwP vaccine, was in the middle of the range of titers observed during other studies using the months schedule conducted with the same vaccine. The consistent immunogenicity of the DTaP 2Fr vaccine is accompanied by effectiveness in controlling pertussis disease in the areas where it is used on a large scale with good vaccination coverage. Introduction Safety, immunogenicity and clinical efficacy trials of various formulations of diphtheria-tetanus-acellular pertussis combination vaccines (DTaP) conducted in the 1990s permitted licensure of vaccines containing from one to five components (or antigens) of Bordetella pertussis. Since then, many of these vaccines have been in extensive clinical use, including several containing the pertussis toxoid (PT) and filamentous haemagglutinin (FHA) antigens. One of these two component vaccines (DTaP 2 ) is manufactured in France (DTaP 2Fr ). Early Phase I and Phase II clinical studies performed in France and the USA with the DTaP 2Fr vaccine documented the doseresponse effect of different vaccine formulations in adults, children, toddlers and infants. 1-6 These studies confirmed earlier ones done in Japan with other DTaP 2 vaccines 7 which concluded that the optimal content of aldehyde-detoxified PT and FHA for such vaccines in a primary series should be about μg each per dose. The DTaP 2Fr vaccine is the core of various combinations with other pediatric vaccine antigens. Marketed combinations include a DTaP-IPV tetravalent vaccine used as a standalone vaccine (Tetravac TM or Tetraxim TM ) or to reconstitute (//) the lyophilized Hib tetanus conjugate (PRP~T) vaccine (ActHIB TM ) to form a pentavalent vaccine (DTaP-IPV//PRP~T; Pentavac TM or Pentaxim TM ) and a hexavalent fully liquid ready-to-inject DTaP-IPV-HepB-PRP~T vaccine (Hexavac TM, license no longer active). This work was undertaken to review all the available immunogenicity data accumulated during both the development (pre-license) and the post-marketing experience of the DTaP 2Fr -containing vaccines. As the results from several studies were never published but were accessible to the authors it was felt that including these data would usefully complement this review. These data will be discussed in light of the efficacy data generated for this vaccine when compared with a highly efficacious whole cell pertussis (wcp) vaccine and of the data on the impact on pertussis disease epidemiology of vaccination programs relying on this vaccine. Data on other licensed DTaP vaccines of similar nature, especially another 2-component (PT & FHA) DTaP vaccine made in Japan and distributed in the USA by sanofi pasteur (Tripedia TM ) will also be discussed. This review will not consider the much discussed relative efficacy data for the various DTaP vaccines containing from one to five components Indeed, several national regulatory authorities and national vaccine advisory bodies have stated that it is inappropriate to judge licensed acp vaccines by the number of components they contain. 11,12 Review Methodology All the data from published and unpublished studies (whether or not sponsored by the manufacturer) performed with any of the various vaccines containing DTaP 2Fr were compiled. The vaccines were administered to infants in a primary immunization series consistent with the immunization practices of the host country and included two doses in the first year of life followed by a toddler booster, or three doses in the first year of life followed also in some studies by a toddler booster. As the studies were conducted over a long period (from 1987 to 2006), the serological assays were performed by various laboratories, *Correspondence to: Stanley A. Plotkin; 4650 Wismer Road; Doylestown, Pennsylvania USA; Tel.: ; Fax: ; Stanley. Plotkin@sanofi-pasteur.com Submitted: 01/21/08; Revised: 03/25/08; Accepted: 04/02/08 Previously published online as a Human Vaccines E-publication: Human Vaccines 2008; Vol. 4 Issue 5

3 including those of the study sponsor, those of national regulatory agencies, and those of academic institutions serving national regulatory agencies. Anti-PT antibodies were determined by Enzyme-Linked Immunoassays (EIA) 13 and in most trials their functional activity were also documented through the CHO cell neutralization assay. 14 Anti-FHA antibodies were determined by EIA. 13 Depending on the laboratory where the assays were performed, the antigens used were of different origins, but for most studies the antigens were purified native PT and purified FHA provided by sanofi pasteur (formerly Pasteur Mérieux Serums & Vaccines and then Aventis Pasteur) and produced by the same process used for manufacturing vaccine antigens. The procedural aspects of EIAs performed in some laboratories were not available, and therefore some outlier results could not be explained (CAMR, UK). For the studies in which sera were assayed by Sanofi Pasteur, concordance studies were conducted to validate assay transfer from the main historical laboratory (Clinical Immunology Platform, Val-de-Reuil, France; CIP-Fr) to the current laboratory (Global Clinical Immunology, Swiftwater, PA, USA, GCI-US). Results obtained from several panels of sera generated in clinical trials and covering the range of expected responses (from less than the lower limit of quantitation (LLOQ) of 2 ELISA Unit (EU)/mL to >1000 EU/mL for EIA anti-pt and anti-fha, and from less than the LLOQ of 2 [1/dil] to 512 [1/dil] for anti-pt measured by the CHO cell neutralization assay) demonstrated good concordance and validity of the results generated from the two laboratories (data not shown). For each trial, the data were considered on a study group basis. For each study group, the respective geometric mean antibody concentration or titer (GMT) and proportion of subjects responding with a 4 fold-rise in their antibody titers from pre-dose 1 to post-dose 3 were reported, as these two parameters are widely used to evaluate immune responses to these antigens in the absence of an undisputed serologic correlate of protection for pertussis. When available, antibody titers for B. pertussis agglutinins were also reported. Studies Reviewed We identified a total of 75 study groups from 36 clinical trials conducted in 17 countries [Western Europe (France, UK, Germany, Spain, Belgium, Italy, Sweden), Central Europe (Turkey), North America (USA), South America (Chile, Argentina), Africa (Sénégal, South African Republic), and South East Asia (Vietnam, Thailand, Philippines, India)] since Overall, these trials included nearly 10,000 subjects. The studies are listed in Table 1, and their main design characteristics are presented in Tables 2, 3 and 4 along with the responses to the PT and FHA antigens. Among the trials identified, one (Study 6) was the Phase III Sénégal Pertussis Relative Efficacy Trial (the Sénégal Trial) in which the relative efficacy of DTaP 2Fr was evaluated compared with the French DTwP vaccine. A comparative immunogenicity study was nested in it. In addition, two randomized comparative trials (RCT) sponsored by other pharmaceutical companies were performed using a DTaP 2Fr -containing licensed vaccine either as the concomitant vaccine (Study 26) or as the comparator vaccine (Study 29). Overall Immunogenicity Profile Post-dose 3 antibody responses to PT and FHA antigens are presented in Tables 2, 3 and 4 with the GMT and the percentages of Table 1 Characteristics of clinical trials reviewed Study Study code References Country Sponsor Year of conduct 1 E2X , 60 USA Mérieux Institute DTC France Mérieux Institute P3M Sénégal Mérieux Institute P3M USA US NIH P3M UK UK MRC & DoH DTC Sénégal Pasteur Mérieux E2I Sénégal Pasteur Mérieux E2X Belgium & Pasteur Mérieux Turkey 9 E2X UK Pasteur Mérieux E2X Vietnam Pasteur Mérieux TET France Mérieux Institute E2I France Pasteur Mérieux E2I France Pasteur Mérieux E2I Sweden Pasteur Mérieux E2I Chile Pasteur Mérieux E2I USA Pasteur Mérieux E2I Turkey Pasteur Mérieux A3R France Pasteur Mérieux A3R France Pasteur Mérieux A3R France Pasteur Mérieux A3R Chile Pasteur Mérieux A3R France Pasteur Mérieux A3R Sweden Pasteur Mérieux E2I Germany Pasteur Mérieux MSD 25 A3R Germany & Pasteur Mérieux Belgium 26 NA 84 Germany & Wyeth Lederle 2001 France Vaccines 27 A3R23 85 Spain Pasteur Mérieux MSD 28 A3R25 86 South African Aventis Pasteur Republic 29 NA 25 Germany GSK A3R21 87 Italy Aventis Pasteur MSD 31 A3R31 88 Thailand Aventis Pasteur E2I29 89 Philippines Aventis Pasteur A3L02 90 Argentina Aventis Pasteur E2I41 91 India Sanofi Pasteur E2I43 92 South African Sanofi Pasteur 2006 Republic 36 E2I34 93 Thailand Sanofi Pasteur 2006 subjects in each study group achieving 4-fold rise in their antibody titers. As pointed out earlier, serological results presented in these tables were generated in different laboratories, thus introducing possible interlaboratory variability of clinical assay data, which might challenge the comparison of results from one study to another. To reduce this limitation, and to facilitate data interpretation, only the results of studies in which the sera were assayed in either of the Human Vaccines 329

4 Table 2 Post-dose 3 responses against PT (EIA) in infants vaccinated with DTaP 2Fr -containing vaccines Study Vaccine Lot number Laboratory Country Schedule and concomitantly Post-dose 3 responses administered vaccines N GMT % 4x-rise 1 DTaP S1794 Vand. Univ., USA USA %* 4 DTaP S2112 CBER (GSK Ag) USA % KI, Sweden NA 65 NA CIP-Fr (VdR) NA 65 NA 5 DTaP NA CAMR, UK UK % S with Act-Hib and OPV % 6 DTaP S2112, S2301, CIP-Fr (VdR) Sénégal with IPV NA S2684, S DTaP S2964 CIP-Fr (VdR) Sénégal with BCG at 2 months % with BCG at 1 month % with BCG at 1 month % 8 DTaP S2938 CIP-Fr (VdR) Belgium with Act-Hib % with Act-Hib % reconstituting Act-Hib % Turkey with Act-Hib % with Act-Hib % reconstituting Act-Hib % 9 DTaP S2938 CIP-Fr (VdR) UK reconstituting Act-Hib with OPV % S % S % S2938, S2957, CAMR, UK NA S DTaP S3424 CIP-Fr (VdR) Vietnam reconstituting Act-Hib with OPV % with Act-Hib with OPV % with Act-Hib with OPV % 12 DTaP-IPV S2956 CIP-Fr (VdR) France with Act-Hib % S % S % S reconstituting Act-Hib % S % S % 13 DTaP-IPV S3028 CIP-Fr (VdR) France reconstituting Act-Hib % reconstituting Act-Hib % 14 DTaP-IPV S3028, S2965 CIP-Fr (VdR) Sweden reconstituting Act-Hib % (for 12) reconstituting Act-Hib %** 15 DTaP S2938 CIP-Fr (VdR) Chile with OPV % with IPV % DTaP-IPV S with Act-Hib at % with Act-Hib % reconstituting Act-Hib % 16 DTaP S2938 CIP-Fr (VdR) USA with Act-Hib and OPV % DTaP-IPV S with Act-Hib % reconstituting Act-Hib % 17 DTaP-IPV S2965 CIP-Fr (VdR) Turkey reconstituting Act-Hib with % HepB concomitantly 18 DTaP-IPV-PRP-T/HepB S3041 CIP-Fr (VdR) France % DTaP-IPV-HepB-PRP-T S % 19 DTaP-PRP-T/HepB S3040 CIP-Fr (VdR) Belgium with OPV % DTaP-HepB-PRP-T S % 20 DTaP-IPV-HepB-PRP-T S3128 CIP-Fr (VdR) France % DTaP-IPV S reconstituting Act-Hib with HepB % 21 DTaP-IPV-HepB-PRP-T S3127 CIP-Fr (VdR) Chile % S % S % 22 DTaP-IPV-HepB-PRP-T S3127 CIP-Fr (VdR) France % % 23 DTaP-IPV-HepB-PRP-T S3595 CIP-Fr (VdR) Sweden %** 330 Human Vaccines 2008; Vol. 4 Issue 5

5 Table 2 Post-dose 3 responses against PT (EIA) in infants vaccinated with DTaP 2Fr -containing vaccines (continued) Study Vaccine Lot number Laboratory Country Schedule and concomitantly Post-dose 3 responses administered vaccines N GMT % 4x-rise 24 DTaP-IPV N1191 CIP-Fr (VdR) Germany concomitantly with Comvax % (HepB-PRP-OMP) 25 DTaP-IPV-HepB-PRP-T S3616 CIP-Fr (VdR) Ger./Belg % (with HepA vaccination at % 6 months) 26 DTaP-IPV-HepB-PRP-T 1 commercial WL Lab Ger./Fr with 7v-PnC 131 NA 96.7%* batch (Rochester, US) with 7v-PnC at NA 96.8%* 27 DTaP-IPV//PRP-T T0227, T1479 CIP-Fr (VdR) Spain (with HepB vaccination at birth) NA DTaP-IPV-HepB-PRP-T T0408, U NA Mixed schedule NA (H-P-H) 28 DTaP-IPV-HepB-PRP-T U0228 CIP-Fr (VdR) RSA weeks (with HepB % vaccination at birth) weeks (with no HepB % vaccination at birth) 29 DTaP-IPV-HepB-PRP-T 1 commercial GSK, Belgium Germany %*** batch 30 DTaP-IPV-HepB-PRP-T T0518, U1130, CIP-Fr (VdR) Italy (with MMR vaccination %** W0386 at 12 months) %** 31 DTaP-IPV-HepB-PRP-T W0386 GCI US Thailand % 32 DTaP-IPV//PRP-T W1538 GCI US Philippines weeks (with HepB at % weeks) weeks (with HepB at % weeks) 33 DTaP-IPV-HepB-PRP-T PFAGI GCI US Argentina % DTaP-IPV//PRP-T X with HepB % 34 DTaP-IPV//PRP-T Z GCI US India weeks (with HepB at % / weeks) 35 DTaP-IPV//PRP-T Z GCI US RSA weeks (with HepB at % weeks) 36 DTaP-IPV//PRP-T Z GCI US Thailand (with HepB at % months of age) *2-fold-rise; **versus pre-dose 3 levels; ***response rate defined as post-dose 3 titer above 5 EU/mL. NA: not available. two sanofi pasteur laboratories (CIP-Fr and GCI-US) are displayed graphically on Figure 1. As concordance studies validated the transfer from the historical laboratory (CIP-Fr) to the new laboratory (GCI-US) and as at each laboratory control charts and good laboratory practices requirements were in force at the time of assay execution, assay performance drifts were minimized. The study arms are grouped according to the primary series regimen used ( months, months, 2-3-4/3-4-5 months and the EPI schedule) used and the region where the study was performed (European Union, North America or rest of the world). Overall, depending on the study group, post-dose 3 GMTs ranged from 49 to 184 EU/mL for anti-pt EIA responses, 17.6 to 114 (1/dil) for anti-pt CHO responses, and 95 to 293 EU/mL for anti-fha EIA responses. The main source of variability in responses was the primary series schedule. The region where the study was performed also influenced immune responses, though to a much lower extent, suggesting the importance of ethno-ecological factors. In addition, the inclusion of other antigens in the DTaP 2Fr -based combination vaccines was not a source of variability. When considering the immunological criterion most often used to demonstrate statistical non-inferiority between vaccines in RCT, namely the proportions of subjects reaching a 4-fold-rise in their antibody titers from pre-dose 1 to post-dose 3, the responses showed less variability (Fig. 1). It should be noted that for the schedule (the so-called schedule), the percentages of 4 fold-risers included in the tables and in Figure 1 were calculated between post-dose 2 and post-dose 3 titers (rather than between post-dose 1 and post-dose 3 titers), therefore minimizing the response rates compared to the other schedules. Percentages ranged from 80% to 100% for anti-pt EIA responses, and 71.3% to 100% for anti-fha EIA responses. Anti-PT CHO responses were much more variable with percentages ranging from 11.5% to 88%. Immune responses observed in the efficacy trial. During the Sénégal Trial (Study 6) sera obtained from approximately 140 infants per group were analyzed in the same laboratory as the majority of the other studies reviewed herein (CIP-Fr). The immune responses against PT and FHA observed in that trial (107 EU/mL for anti-pt EIA responses, 56 1/dil for anti-pt CHO responses, and 235 EU/mL for anti-fha EIA responses) were in the middle of the range of titers observed during other studies conducted with the DTaP 2Fr vaccines used with the month schedule, as illustrated in Figure 1. Human Vaccines 331

6 Table 3 Post-dose 3 responses against PT (CHO assay) in infants vaccinated with DTaP 2Fr -containing vaccines Study Vaccine Lot number Laboratory Country Schedule and concomitantly Post-Dose 3 administered vaccines N GMT % 4x-rise 1 DTaP S1794 St.Ch.Hosp., PA, USA USA % 2 DTaP S1972 QC lab, MLE France % 3 DTaP S2112 QC lab, MLE Sénégal % 4 DTaP S2112 St.Ch.Hosp., PA USA % CIP-Fr (VdR) NA KI, Stockolm, Sw % 6 DTaP S2112, S2301, CIP-Fr (VdR) Sénégal with IPV NA S2684, S DTaP S2964 KI, Stockolm, Sw Sénégal with BCG at 2 months % with BCG at 1 month % with BCG at 1 month % 8 DTaP S2938 CIP-Fr (VdR) Belgium with Act-Hib % with Act-Hib % reconstituting Act-Hib % Turkey with Act-Hib % with Act-Hib % reconstituting Act-Hib % 9 DTaP S2938 CIP-Fr (VdR) UK reconstituting Act-Hib with OPV % S % S % 10 DTaP S3424 CIP-Fr (VdR) Vietnam reconstituting Act-Hib with OPV % with Act-Hib with OPV % with Act-Hib with OPV % 11 DTaP-IPV S1973 QC lab, IM France % 12 DTaP-IPV S2956 CIP-Fr (VdR) France with Act-Hib % S % S % S reconstituting Act-Hib % S % S % 13 DTaP-IPV S3028 CIP-Fr (VdR) France reconstituting Act-Hib % reconstituting Act-Hib % 14 DTaP-IPV S3028, S2965 KI, Stockolm, Sw Sweden reconstituting Act-Hib NA (12 months) reconstituting Act-Hib NA CIP-Fr (VdR) reconstituting Act-Hib NA reconstituting Act-Hib NA 15 DTaP S2938 CIP-Fr (VdR) Chile with OPV % with IPV % DTaP-IPV S % with Act-Hib % reconstituting Act-Hib % 16 DTaP S2938 CIP-Fr (VdR) USA with Act-Hib and OPV % DTaP-IPV S with Act-Hib % reconstituting Act-Hib % 17 DTaP-IPV S2965 CIP-Fr (VdR) Turkey reconstituting Act-Hib with % HepB concomitantly 18 DTaP-IPV-PRP-T/HepB S3041 CIP-Fr (VdR) France NA DTaP-IPV-HepB-PRP-T S % 19 DTaP-PRP-T/HepB S3040 CIP-Fr (VdR) Belgium with OPV % DTaP-HepB-PRP-T S % 20 DTaP-IPV-PRP-T-HepB S3128 CIP-Fr (VdR) France % DTaP-IPV S reconstituting Act-Hib % with HepB 21 DTaP-IPV-PRP-T-HepB S3127 CIP-Fr (VdR) Chile % S % S % 22 DTaP-IPV-PRP-T-HepB S3127 CIP-Fr (VdR) France % % 332 Human Vaccines 2008; Vol. 4 Issue 5

7 Table 3 Post-dose 3 responses against PT (CHO assay) in infants vaccinated with DTaP 2Fr -containing vaccines (continued) Study Vaccine Lot number Laboratory Country Schedule and concomitantly Post-Dose 3 administered vaccines N GMT % 4x-rise 23 DTaP-IPV-PRP-T-HepB S3595 CIP-Fr (VdR) Sweden %** 25 DTaP-IPV-PRP-T-HepB S3616 CIP-Fr (VdR) Ger./Belg % (with HepA vaccination % at 6 months) 28 DTaP-IPV-PRP-T-HepB U0228 CIP-Fr (VdR) RSA EPI ( weeks) HepB % vaccination at birth EPI ( weeks) No HepB % vaccination at birth 30 DTaP-IPV-PRP-T-HepB T0518, U1130, CIP-Fr (VdR) Italy (with MMR vaccination %** W0386 at 12 months) %** *2-fold-rise; **versus pre-dose 3 levels; ***response rate defined as post-dose 3 titer above 5 EU/mL. NA: not available. Table 4 Post-dose 3 responses against FHA (EIA) in infants vaccinated with DTaP 2Fr -containing vaccines Study Vaccine Lot number Laboratory Country Schedule and concomitantly Post-dose 3 responses administered vaccines N GMT % 4x-rise 1 DTaP S1794 Vand. Univ., USA USA %* 2 DTaP S1972 QC lab, MLE France % 3 DTaP S2112 QC lab, MLE Sénégal % 4 DTaP S2112 CBER (SPAg) USA % 5 DTaP NA CAMR, UK UK % S with Act-Hib and OPV % 6 DTaP S2112, S2301, CIP-Fr (VdR) Sénégal with IPV NA S2684, S DTaP S2964 CIP-Fr (VdR) Sénégal with BCG at 2 months NA with BCG at 1 month NA with BCG at 1 month NA 8 DTaP S2938 CIP-Fr (VdR) Belgium with Act-Hib % with Act-Hib % reconstituting Act-Hib % with Act-Hib % Turkey with Act-Hib % reconstituting Act-Hib % 9 DTaP S2938 UK reconstituting Act-Hib with OPV % S2957 CIP-Fr (VdR) % S % S2938, S2957, CAMR, UK NA S DTaP S3424 CIP-Fr (VdR) Vietnam reconstituting Act-Hib with OPV % with Act-Hib with OPV % with Act-Hib with OPV % 11 DTaP-IPV S1973 QC lab, MLE France % 12 DTaP-IPV S2956 CIP-Fr (VdR) France with Act-Hib % S % S % S % S reconstituting Act-Hib % S % 13 DTaP-IPV S3028 CIP-Fr (VdR) France reconstituting Act-Hib % reconstituting Act-Hib % 14 DTaP-IPV S3028, S2965 CIP-Fr (VdR) Sweden reconstituting Act-Hib % (for 12) reconstituting Act-Hib %** Human Vaccines 333

8 Table 4 Post-dose 3 responses against FHA (EIA) in infants vaccinated with DTaP 2Fr -containing vaccines (continued) Study Vaccine Lot number Laboratory Country Schedule and concomitantly Post-dose 3 responses administered vaccines N GMT % 4x-rise 15 DTaP S2938 CIP-Fr (VdR) Chile with OPV % with IPV % DTaP-IPV S with Act-Hib at % with Act-Hib % reconstituting Act-Hib % 16 DTaP S2938 CIP-Fr (VdR) USA with Act-Hib and OPV % DTaP-IPV S with Act-Hib % reconstituting Act-Hib % 17 DTaP-IPV S2965 CIP-Fr (VdR) Turkey reconstituting Act-Hib with % HepB concomitantly 18 DTaP-IPV-PRP-T/HepB S3041 CIP-Fr (VdR) France % DTaP-IPV-HepB-PRP-T S % 19 DTaP-PRP-T/HepB S3040 CIP-Fr (VdR) Belgium with OPV % DTaP-HepB-PRP-T S % 20 DTaP-IPV-HepB-PRP-T S3128 CIP-Fr (VdR) France % DTaP-IPV S reconstituting Act-Hib % with HepB 21 DTaP-IPV-HepB-PRP-T S3127 CIP-Fr (VdR) Chile % S % S % 22 DTaP-IPV-HepB-PRP-T S3127 CIP-Fr (VdR) France % % 23 DTaP-IPV-HepB-PRP-T S3595 CIP-Fr (VdR) Sweden %** 24 DTaP-IPV N1191 CIP-Fr (VdR) Germany concomitantly with Comvax % (HepB-PRP-OMP) 25 DTaP-IPV-HepB-PRP-T S3616 CIP-Fr (VdR) Ger./Belg % (with HepA vaccination % at 6 months) 26 DTaP-IPV-HepB-PRP-T 1 commercial WL Lab Ger./Fr with 7v-PnC 131 NA 93.4%** batch (Rochester, US) with 7v-PnC at NA 96.8%** 27 DTaP-IPV//PRP-T T0227, T1479 CIP-Fr (VdR) Spain (with HepB vaccination NA at birth) DTaP-IPV-HepB-PRP-T T0408, U NA Mixed schedule NA (H-P-H) 28 DTaP-IPV-HepB-PRP-T U0228 CIP-Fr (VdR) RSA weeks (with HepB % vaccination at birth) weeks (with no HepB % vaccination at birth) 29 DTaP-IPV-HepB-PRP-T 1 commercial GSK, Belgium Germany %*** batch 30 DTaP-IPV-HepB-PRP-T T0518, U1130, CIP-Fr (VdR) Italy (with MMR vaccination %** W0386 at 12 months) %** 31 DTaP-IPV-HepB-PRP-T W0386 GCI US Thailand % 32 DTaP-IPV//PRP-T W1538 GCI US Philippines weeks (with HepB at % weeks) weeks (with HepB at % weeks) 33 DTaP-IPV-HepB-PRP-T PFAGI GCI US Argentina % DTaP-IPV//PRP-T X with HepB % 34 DTaP-IPV//PRP-T Z GCI US India weeks (with HepB at % / weeks) 35 DTaP-IPV//PRP-T Z GCI US RSA weeks (with HepB at % weeks) 36 DTaP-IPV//PRP-T Z GCI US Thailand (with HepB at % months of age) *2 fold-rise; **versus pre-dose 3 levels; ***response rate defined as post-dose 3 titer above 5 EU/mL. NA: not available. 334 Human Vaccines 2008; Vol. 4 Issue 5

9 Table 5 Post-dose 3 responses in infants vaccinated with DTaP 2Fr -containing vaccines compared to DTwP vaccines Study Vaccine Schedule and concomitantly Assays Post-dose 3 responses administered vaccines N GMT % 4x-rise 1 DTaP with OPV Pertussis Agglutinins %* Anti-PT (EIA) 56 97%* Anti-PT (CHO Neut. Assay) 20 68% Anti-FHA (EIA) %* DTwP (Welcome) Pertussis Agglutinins %* Anti-PT (EIA) 60 85%* Anti-PT (CHO Neut. Assay) 12 56% Anti-FHA (EIA) 11 50%* 3 DTaP with IPV Anti-PT (CHO Neut. Assay) % Anti-FHA (EIA) % DTwP (sanofi pasteur Fr) Anti-PT (CHO Neut. Assay) % Anti-FHA (EIA) % 4 DTaP with OPV Pertussis Agglutinins % Anti-PT (EIA) % Anti-PT (CHO Neut. Assay) % Anti-FHA (EIA) % DTwP (Welcome) Pertussis Agglutinins % Anti-PT (EIA) % Anti-PT (CHO Neut. Assay) % Anti-FHA (EIA) % 5 DTaP Anti-PT (EIA) % Anti-FHA (EIA) % DTwP (Welcome) Anti-PT (EIA) % Anti-FHA (EIA) % DTaP with Act-Hib and OPV Anti-PT (EIA) % Anti-FHA (EIA) % DTwP (Welcome) Anti-PT (EIA) % Anti-FHA (EIA) % 6 DTaP with IPV Anti-PT (EIA) NA Anti-PT (CHO Neut. Assay) 56 Anti-FHA (EIA) 235 DTwP (sanofi pasteur Fr) Anti-PT (EIA) NA Anti-PT (CHO Neut. Assay) 57 Anti-FHA (EIA) DTaP Anti-PT (EIA) NA Anti-FHA (EIA) DTwP (sanofi pasteur Fr) Anti-PT (EIA) NA Anti-FHA (EIA) DTaP-IPV Anti-PT (CHO Neut. Assay) % Anti-FHA (EIA) % DTwP-IPV (sanofi pasteur Fr) Anti-PT (CHO Neut. Assay) % Anti-FHA (EIA) % *2-fold-rise, NA: not available. Two of the four DTaP 2Fr vaccine lots used in the Sénégal Trial were used in six other trials. Lot S2112 was used in Sénégal (Study 3) and in the USA (Study 4); and Lot S2938 was used in Belgium and Turkey (Study 8), the UK (Study 9), Chile (Study 15), and in the USA (Study 16). Immune responses obtained with these two DTaP 2Fr lots, when given with the same schedule and evaluated in the same laboratories, were within the range of the responses observed during the Sénégal Trial (post-dose 3 GMTs ranged from 65 to 130 EU/mL for anti-pt EIA responses, 42 to /dil for anti-pt CHO responses, and 135 to 254 EU/mL for anti-fha EIA responses). Comparison with whole-cell vaccines. Seven of the identified studies compared DTaP 2Fr -containing vaccines with three different wcp-containing vaccines (Studies 1, 3 6, 9 and 11). Study 9 was not a true RCT as the DTaP 2Fr was compared with a DTwP Fr included in a study conducted contemporaneously in the same trial center and where sera were tested in the same laboratory with the same assay. 15 Serological results are presented on Table 5. Anti-PT antibodies as measured by EIA were similar (or even higher) in the DTaP 2Fr vaccine groups and in the DTwP vaccine groups. However, anti-pt responses measured by the CHO cell neutralisation assay were lower, similar or higher than after the DTwP vaccine, varying with the trial and on the CHO cell neutralisation assay used to test the sera and on the nature of the DTwP vaccine used as comparator. The levels of anti-fha antibodies were higher after the DTaP 2Fr vaccine than after the whole cell vaccines in all studies. However, it should be noted that three different wcp vaccines were tested in these studies, differing probably in their respective antigenic content, and the Human Vaccines 335

10 Figure 1. Post-dose 3 GMT and percentage of four-fold rise from pre-dose 1 to post-dose 3 against PT and FHA as measured at sanofi pasteur (CIP-Fr or GCI-US) in infants vaccinated with two-component (PT & FHA) containing vaccines manufactured by sanofi pasteur month schedule (Sweden, Italy) [from post dose 2 to post-dose 3 for % 4-fold rise] month schedule (outside EU and NA) (bolded symbol for the Senegal efficacy trial) month schedule (in EU and NA) or month schedule (outside EU and NA) or month schedule (in EU and NA). EPI schedule (outside EU and NA). assays also differed, complicating the inter-study comparisons, and limiting the relevance of such comparisons. Effect of additional antigens. Responses to PT and FHA antigens obtained with vaccines containing additional valences (DTaP 2Fr ± IPV, Hib, or HepB) revealed no interference, as shown in multiple RCTs (studies 8, 10, 12, 15, 16, 20, 27 and 33). Furthermore, the comparison of the responses obtained with the DTaP 2Fr vaccine co-administered (at separate injection sites) with other vaccines (IPV, Hib, or HepB) showed no detrimental effect on the immune responses against PT and FHA antigens (studies 15 and 20). Long-term persistence of antibodies. Two trials have documented the long-term persistence of antibodies induced by the DTaP 2Fr -containing vaccines following a 3 dose primary series. In the first study (Study 5), performed in the UK under two different primary series schedules (3-5-9 or months of age) without toddler booster vaccination, antibody persistence was evident and a 6- to 15-fold reduction in GMT against PT and FHA was observed compared with the 6 week post-third dose sample when evaluated months post-dose A longer follow-up (up to the age of 4.5 years) of the children given the month primary schedule confirmed this observation with much less reduction in GMTs. 16 In the second study performed in Sweden (Study 14), the longterm persistence (up to 5.5 years of age) of PT and FHA antibodies induced by the DTaP 2Fr -IPV//PRP~T vaccine was similar among children primed with a month schedule compared with children primed with a month schedule. 17 Vaccine Formulation Effect The trials were done with eight different vaccine formulations; three of these have been licensed [DTaP-IPV (Tetravac TM, Tetraxim TM ), DTaP-IPV//PRP~T (Pentavac TM, Pentaxim TM ) and DTaP-IPV-HepB-PRP~T (Hexavac TM )], and one is currently under development (a DTaP-IPV-HepB-PRP~T which differs from Hexavac TM in the origin of its HBsAg valence and its formulation characteristics, Hexaxim TM ). Four combinations were vaccine formulations evaluated during the development programs of the aforementioned licensed vaccines, including the backbone vaccine [DTaP (Triavac TM, Triaxim TM )] and combinations that were never taken to licensure [DTaP//PRP~T; DTaP-PRP~T/HepB (liquid/ liquid in a dual-chambered by-pass syringe); and DTaP-IPV-PRP~T/ HepB (liquid/liquid in a dual-chambered by-pass syringe)]. When comparing results from RCT performed in similar settings, with similar vaccination schedules and for which sera were assessed with concordant assays (CIP-Fr and GCI-US), the immune responses against PT and FHA antigens obtained with vaccines containing one or more additional valences (IPV, HepB and/or PRP~T) (studies 8, 10, 12, 15, 16, 20, 27 and 33) were similar to these obtained with the basic DTaP 2Fr vaccine. The conclusion emerging from this compilation is that addition of other valences does not affect the immunogenicity of the PT or FHA antigens contained in the different combination formulations. The opposite effect (i.e., the influence of PT and FHA antigens, or of any other vaccine constituent, on responses to the co-injected antigens) is beyond the scope of this review. However, it is well described that the only antigen affected by such interference is the Hib conjugated polysaccharide. It has been shown that several factors may affect immune responses to this type 336 Human Vaccines 2008; Vol. 4 Issue 5

11 of antigen, including the nature of the specific protein carrier for the Hib polysaccharide, the nature of the aluminum salt adjuvant added to the Hib antigen, the specific formulation characteristics of the combination vaccine, the ethno-ecological status of the vaccinees, and the primary series schedule It is clear that the variability of the anti-prp responses in combination vaccines made of DTaP- Hib that is observed in randomized controlled trials of DTaP-Hib has been a major cause of licensure delays or even non-licensure by some regulatory authorities. This has been the case for DTaP 2Fr -Hib in some countries. However, in the circumstance of high vaccine coverage and administration of a fourth dose in the second year of life, the DTaP 2Fr -Hib based combinations, where licensed, demonstrated effectiveness for all of its components, and the potential problem with Hib has not arisen. Finally, the immunogenicity profile of the vaccines used in the most recent studies compared favorably with early studies done with vaccines manufactured 15 years ago, documenting consistent production of antigens over time, including successive scale-up and improvements of the manufacturing processes and release assays that inevitably occur with any product expansion. Schedule Effect As illustrated in Figure 1, the main parameters that affect the intensity of immune responses to PT and FHA were the schedule used for the primary series and to a lesser extent the geographic location of the studies, which may reflect ethno-ecological differences. Among the different regimens, the most immunogenic was the month schedule, followed by the month schedule, the 2-3-4/3-4-5 month schedule and lastly by the EPI schedule ( weeks of age). This has been also observed with other DTaP vaccines, 22 and is not specific to individual pertussis antigens. The same phenomenon is seen with other antigens contained in pediatric combinations It has also to be pointed out that when compared with the other schedules, the schedule can be considered as a two-dose primary series followed by a booster due to the seven months interval between the second and third dose, which therefore explain its better immunogenicity performance. Therefore this schedule cannot be fully compared to the three-dose first year of life primary series schedules. Immunogenicity Comparison Versus Other Licensed DTaP Vaccines There are only a few randomized trials that compared the immunogenicity of DTaP 2Fr -containing vaccines to other licensed acellular pertussis vaccines containing all or some of the same antigens and with similar quantities (20 to 25 μg each). The landmark multicenter acellular pertussis trial sponsored by NIH (Study 4) compared several acellular pertussis vaccines among which some were licensed (DTaP 2Fr, Tripedia TM, Infanrix TM ). For these three licensed vaccines, which share common antigens with similar content, anti-pt responses ranged from 54 EU/mL to 127 EU/mL (GMT) and from 90.7% to 99.2% ( 4-fold rise) and anti-fha responses ranged from 84 EU/mL to 143 EU/mL (GMT) and from 85.6% to 95.0% ( 4-fold rise). 24 This study concluded that when considering vaccines having similar antigen contents no DTaP stood out as being most or least immunogenic. A recently conducted RCT between a DTaP 2Fr -containing vaccine versus a three-component acellular pertussis containing combination vaccine (DTaP 3Bel ) (Study 29) reached the same conclusion. Anti-PT responses were 61.5 EU/ ml and 65.2 EU/mL (GMT) and 97.0% and 98.1% ( 4-fold rise) for the DTaP 2Fr and the DTaP 3Bel vaccines, respectively. Similarly, anti-fha responses were EU/mL and EU/mL (GMT) and 99.0% and 99.1% ( 4-fold rise) for these two DTaP vaccines, respectively. 25 Effect of Antibody Determination Assay Variation A major difficulty in interpreting the data compiled in this review and similar work is that several laboratories were involved in the serological determinations using different enzyme immunoassays or CHO cell neutralization assays. Numerous attempts have been made to standardize the assays of human antibodies to B. pertussis, 26,27 and the use of panels of reference sera has provided some success, but only appropriate studies of precision and quantitative agreement between laboratories will allow better inter-laboratory comparisons. 28 Only the studies in which immunogenicity data were generated in laboratories having undergone documented inter-assay concordance (CIP-Fr and GCI-US, sanofi pasteur data in file) were included in Figure 1. Several studies have shown a good correlation between anti-pt antibody titers measured by EIA and the CHO neutralization assay, 29 therefore reinforcing the suitability of the anti-pt EIA for the evaluation of the immunogenicity of acellular pertussis PT containing vaccines. Nevertheless, the variability of the assays at an individual level and at the study level explain why the responses, when measured as the proportions of subjects responding with a 4-fold-rise in their antibody titers from pre-dose 1 to post-dose 3, were more variable than the post-dose 3 GMTs. Correlation with Cellular Mediated Immune Responses Data The induction of cell-mediated immunity (CMI) against B. pertussis antigens by DTaP vaccines when administered during infancy has been documented on several occasions, particularly in studies nested within the pertussis efficacy trials performed in the 1990s. 30,31 They all have concluded that DTaP vaccines induce Th1-Th2 mixed responses, whereas DTwcP vaccines and natural infection induce Th1-skewed responses. 32,33 CMI data in studies conducted with the DTaP 2Fr -containing vaccines, although not with standardized assays, show that the CMI responses consist of a balanced Th1-Th2 response, similar to responses induced by other ap-vaccines Bridge Between Immunogenicity and Efficacy/Effectiveness A bridge between immunogenicity and efficacy/effectiveness induced by the DTaP 2Fr -containing vaccines can be established through the use of several data sets. This bridge is not made by using the levels of PT or FHA antibodies as individual serological correlates of protection, but rather as disease risk predictors, as has been proposed previously. 37 The Sénégal Trial. The first data set comes from the Sénégal Trial (Study 6) This study was unique in its design; it was a relative efficacy trial in a developing country with a long period of follow up in the absence of booster vaccination in the second year of life. The follow-up period covered a mean duration of 1.79 years (0.01 to 4.25 years) in DTwcP-vaccinated infants (3,165 person-years at risk) and 1.73 years (0.01 to 4.25 years) in DTaP 2Fr -vaccinated infants Human Vaccines 337

12 (3,193 person-years at risk). The antibody titers against PT and FHA measured in the reviewed studies were similar to those measured by the same laboratory in the Sénégal efficacy study. In particular, two of the DTaP 2Fr vaccine lots used in the Sénégal efficacy study gave comparable immune responses in other studies (studies 3, 4, 8, 9, 15 and 16). The overall ratio of pertussis incidence (WHO definition of 21 days of cough plus positive culture, positive serology or contact with a culture-confirmed person) between DTaP 2Fr -vaccinated subjects and DTwcP-vaccinated subjects (RR ac/wc ) was 1.54 (95% CI: ). For children younger than 18 months of age RR ac/wc was 1.16 (95% CI: ) whereas it was 1.76 (95% CI: ) for older children, probably illustrating the effect of the absence of toddler booster vaccination. During that study, a nested household case-contact study was implemented to estimate the absolute vaccine efficacy of the vaccines used. When considering cases with 21 days of paroxysmal cough, the efficacy values were 92% (95% CI: 81 97) for the DTwcP vaccine and 74% (95% CI: 51 86) for the DTaP 2Fr vaccine for the entire follow up period. The use of a more stringent case definition (contact with a PCR-validated culture-confirmed person) led to higher efficacy values: 96% (95% CI: 86 99) for the DTwcP vaccine and 85% (95% CI: 66 93) for the DTaP 2Fr vaccine. It is interesting to note that during long term follow up of the cohorts living in the study area, implemented before and after the execution of this trial, the development of herd immunity against pertussis in unvaccinated infants was also observed. 43 Decreases of 27% and 46% in the crude incidence of 183 per 1,000 child-years at risk under age 5 years before the implementation of the vaccination program were observed after 3 and 6 years of follow up, respectively. The issue of shorter duration of the pertussis protection in the absence of a booster dose administered during the second year of life is not specific to the DTaP 2Fr vaccine. The Sénégal efficacy study was unique among all the pertussis vaccine efficacy trials, not that this was the only one in which a DTaP vaccine was compared with a highly efficacious wcp vaccine 44,45 but rather that this was the only one in which the observation of pertussis cases during the follow up period was implemented in the absence of booster vaccination administered during the second year of life. This type of study design was not implemented during the other pertussis vaccines efficacy trials, and one can only speculate on how such vaccines would have performed in this type of study design. Field experience. Further evidence relates to the results of the routine pertussis vaccination program that is in place in Sweden since 1997, where two acellular pertussis-containing vaccines have been used, of which one is a DTaP 2Fr -containing product. Sweden uses an immunization schedule at months. Since the implementation of this program, the Swedish Institute for Infectious Disease Control has monitored its effectiveness. 46,47 Contrary to previously expressed opinion, 48 the data from Sweden demonstrate that in those counties where it was used exclusively, DTaP 2Fr vaccine decreased the incidence of pertussis disease to a similar extent to that observed in the counties where another acellular pertussis vaccine was exclusively used over the same period of follow up. 49,50 In the DTaP 2Fr vaccine cohorts (accounting for 40% of the approximately 3,386 million personyears of follow up accumulated between July 1997 and September 2006), a considerable reduction was observed in the incidence rates of cultured confirmed cases of pertussis ( 21 days of paroxysmal cough), compared with before the program initiation where the peak incidence in the pre-1996 era was approximately 1,600 cases per 100,000 person-years for children 2 4 years of age. As an example, the incidence between the first dose (3 months) and the second dose (5 months) was 191 per 100,000 person-years, decreasing to 19 per 100,000 person-years between the second dose (5 months) and the third dose (12 months), and being further decreased to 10 cases per 100,000 person-years after the third dose (12 months). Although the use of two different pertussis vaccines varied with birth cohorts and geographic areas, the reported incidence in the total population aggregating data from pure- or mixed-vaccine vaccinated cohorts was similar: 20 cases per 100,000 person-years between the second dose (5 months) and the third dose (12 months) and 11 cases per 100,000 person-years after dose 3. As expected, regardless of the vaccine used and across the population, this surveillance program is detecting waning of vaccine-induced protection in older children that justifies the implementation of additional pre-school and/or adolescent pertussis boosters. 51 Experience obtained in the USA with another licensed twocomponent (PT & FHA) acellular pertussis vaccine (Tripedia TM ) also provides reassuring evidence of effectiveness of two component DTaP vaccines when administered following the North American immunization schedule (2-4-6 months, followed by further boosters), comparing favorably with other acellular vaccines. 52 The antigen content and immunogenicity profile of this vaccine is quite similar to that observed with the DTaP 2Fr vaccine. 53,54 Finally, the Japanese experience also contributes to evidence of effectiveness. In Japan, three types of DTaP vaccines have been used since 1981: the T-type being a FHA dominant vaccine with lower amount of PT, and trace amounts of PRN and Fim2, the B-type being a balanced PT and FHA vaccine with undocumented presence of additional antigens, and a true 2-component PT/FHA vaccine (FHA dominant). 55 Available epidemiological data demonstrate the good control of pertussis disease in Japan. 56,57 The transposition of these observations to developing countries where the force of transmission is expected to be higher than in Sweden, USA and Japan needs nevertheless to be made with caution, and the implementation of a second year of life booster following the first year of life primary series will probably be one of the ways to overcome the effects of higher force of transmission. Conclusion These data confirm that the licensed two-component PT & FHA acellular vaccines are very effective in controlling pertussis disease in the areas where they have been employed on a large scale with good vaccination coverage, and that such vaccines meet current standards for protection against pertussis. The use of two component DTaP vaccines under such conditions is considered by WHO as equivalent to others in pertussis vaccination programs. 58 The data compiled in this document confirm the immunogenicity of the DTaP 2Fr - containing vaccines, which has been associated with effectiveness against pertussis disease. More and more countries are implementing routine vaccination programs relying on ap-based vaccines in order to benefit from their improved safety. With the growing availability of licensed multivalent combination vaccines incorporating Hib, poliomyelitis and hepatitis B antigens, it is anticipated that the use of such products will expand in the future. 338 Human Vaccines 2008; Vol. 4 Issue 5