Clinical Pharmacology for Adacel
Mechanism Of Action
Tetanus
Tetanus is a disease manifested primarily by neuromuscular dysfunction caused by a potent exotoxin released by C tetani.
Protection against disease is due to the development of neutralizing antibodies to tetanus toxin. A serum tetanus antitoxin level of at least 0.01 IU/mL, measured by neutralization assay is considered the minimum protective level. (5) (6)
Diphtheria
Diphtheria is an acute toxin-mediated disease caused by toxigenic strains of C diphtheriae. Protection against disease is due to the development of neutralizing antibodies to diphtheria toxin. A serum diphtheria antitoxin level of 0.01 IU/mL is the lowest level giving some degree of protection. Antitoxin levels of at least 0.1 IU/mL are generally regarded as protective. (5) Levels of 1.0 IU/mL have been associated with long-term protection. (7)
Pertussis
Pertussis (whooping cough) is a respiratory disease caused by B pertussis. This Gram-negative coccobacillus produces a variety of biologically active components, though their role in either the pathogenesis of, or immunity to, pertussis has not been clearly defined.
Clinical Studies
The effectiveness of the tetanus toxoid and diphtheria toxoid used in Adacel was based on the immune response to these antigens compared to a US licensed Tetanus and Diphtheria Toxoids Adsorbed For Adult Use (Td) vaccine manufactured by Sanofi Pasteur Inc., Swiftwater, PA. The primary measures for immune response to the diphtheria and tetanus toxoids were the percentage of participants attaining an antibody level of at least 0.1 IU/mL.
The effectiveness of the pertussis antigens used in Adacel was evaluated based on a comparison of pertussis antibody levels achieved in recipients of Adacel with those obtained in infants after three or four doses of DAPTACEL. For the first dose of Adacel, the comparisons were to infants who received three doses of DAPTACEL in the Sweden I Efficacy trial. For the second dose of Adacel, for the evaluation of FHA, PRN, and FIM antibody levels, the comparisons were to infants who received three doses of DAPTACEL in the Sweden I Efficacy trial; for evaluation of PT antibody levels, the comparison was to infants who received four doses of DAPTACEL in a US safety and immunogenicity study (Study NCT00255047). In the Sweden I Efficacy Trial, three doses of DAPTACEL vaccine were shown to confer a protective efficacy of 84.9% (95% CI: 80.1%, 88.6%) against WHO defined pertussis (21 days of paroxysmal cough with laboratory-confirmed B pertussis infection or epidemiological link to a confirmed case). The protective efficacy against mild pertussis (defined as at least one day of cough with laboratory-confirmed B pertussis infection) was 77.9% (95% CI: 72.6%, 82.2%). (8)
In addition, the ability of Adacel to elicit a booster response (defined as rise in antibody concentration after vaccination) to the tetanus, diphtheria and pertussis antigens following vaccination was evaluated.
Immunological Evaluation In Adolescents And Adults, 11 Through 64 Years Of Age Following A First Vaccination With Adacel (Td506)
Study Td506 was a comparative, multi-center, randomized, observer-blind, controlled trial which enrolled 4,480 participants; 2,053 adolescents (11-17 years of age) and 2,427 adults (18-64 years of age). Enrollment was stratified by age to ensure adequate representation across the entire age range. Participants had not received a tetanus or diphtheria toxoid containing vaccine within the previous 5 years. After enrollment participants were randomized to receive one dose of either Adacel or Td vaccine. A total of 4,461 randomized participants were vaccinated. The per-protocol immunogenicity subset included 1,270 Adacel recipients and 1,026 Td vaccine recipients. Sera were obtained before and approximately 35 days after vaccination. [Blinding procedures for safety assessments are described in ADVERSE REACTIONS.]
Demographic characteristics were similar within age groups and between the vaccine groups. A total of 76% of the adolescents and 1.1% of the adults reported a history of receiving 5 previous doses of diphtheria-tetanus-pertussis containing vaccines. Anti-tetanus and anti-diphtheria seroprotection rates (≥0.1 IU/mL) and booster response rates were comparable between Adacel and Td vaccines. (See Table 4 and Table 5.) Adacel induced pertussis antibody levels that were non-inferior to those of Swedish infants who received three doses of DAPTACEL vaccine (Sweden I Efficacy Study). (See Table 6.) Acceptable booster responses to each of the pertussis antigens were also demonstrated, i.e., the percentage of participants with a booster response exceeded the predefined lower limit. (See Table 7.)
Table 4: Pre-vaccination and Post-vaccination Antibody Responses and Booster Response Rates to Tetanus Toxoid Following a First Vaccination with Adacel Vaccine as Compared to Td Vaccine in Adolescents and Adults 11 through 64 Years of Age (Td506)
|
Anti-Tetanus toxoid
(IU/mL)
Pre-vaccination |
Anti-Tetanus toxoid
(IU/mL)
Pre-vaccination |
Anti-Tetanus toxoid
(IU/mL)
1 Month Post-vaccination |
Anti-Tetanus toxoid
(IU/mL)
1 Month Post-vaccination |
Anti-Tetanus toxoid
(IU/mL)
1 Month Post-vaccination |
| Age Group (years) |
Vaccine |
N* |
% ≥0.10
(95% CI) |
% ≥1.0
(95% CI) |
% ≥0.10
(95% CI) |
% ≥1.0
(95% CI) |
% Booster†
(95% CI) |
| 11-17 |
Adacel |
527 |
99.6
(98.6, 100.0) |
44.6
(40.3, 49.0) |
100.0‡
(99.3, 100.0) |
99.6§
(98.6, 100.0) |
91.7‡
(89.0, 93.9) |
| 11-17 |
Td¶ |
516 |
99.2
(98.0, 99.8) |
43.8
(39.5, 48.2) |
100.0
(99.3, 100.0) |
99.4
(98.3, 99.9) |
91.3
(88.5, 93.6) |
| 18-64 |
Adacel |
742-743 |
97.3
(95.9, 98.3) |
72.9
(69.6, 76.1) |
100.0‡
(99.5, 100.0) |
97.8§
(96.5, 98.8) |
63.1‡
(59.5, 66.6) |
| 18-64 |
Td¶ |
509 |
95.9
(93.8, 97.4) |
70.3
(66.2, 74.3) |
99.8
(98.9, 100.0) |
98.2
(96.7, 99.2) |
66.8
(62.5, 70.9) |
* N = number of participants in the per-protocol population with available data.
† Booster response is defined as: A 4-fold rise in antibody concentration, if the pre-vaccination concentration was equal to or below the cut-off value and a 2-fold rise in antibody concentration if the pre-vaccination concentration was above the cut-off value. The cut-off value for tetanus was 2.7 IU/mL.
‡ Seroprotection rates at ≥0.10 IU/mL and booster response rates to Adacel were non-inferior to Td vaccine (upper limit of the 95% CI on the difference for Td vaccine minus Adacel <10%).
§ Seroprotection rates at ≥1.0 IU/mL were not prospectively defined as a primary endpoint.
¶ Tetanus and Diphtheria Toxoids Adsorbed manufactured by Sanofi Pasteur Inc., Swiftwater, PA. |
Table 5: Pre-vaccination and Post-vaccination Antibody Responses and Booster Response Rates to Diphtheria Toxoid Following a First Vaccination with Adacel as Compared to Td Vaccine in Adolescents and Adults 11 through 64 Years of Age (Td506)
|
Anti-Diphtheria toxin
(IU/mL)
Pre-vaccination |
Anti-Diphtheria toxin
(IU/mL)
Pre-vaccination |
Anti-Diphtheria toxin
(IU/mL)
1 Month Post-vaccination |
Anti-Diphtheria toxin
(IU/mL)
1 Month Post-vaccination |
Anti-Diphtheria toxin
(IU/mL)
1 Month Post-vaccination |
| Age Group (years) |
Vaccine |
N* |
% ≥0.10 (95% CI) |
% ≥1.0 (95% CI) |
% ≥0.10 (95% CI) |
% ≥1.0 (95% CI) |
% Booster† (95% CI) |
| 11-17 |
Adacel |
527 |
72.5
(68.5, 76.3) |
15.7
(12.7, 19.1) |
99.8‡
(98.9, 100.0) |
98.7§
(97.3, 99.5) |
95.1‡
(92.9, 96.8) |
| 11-17 |
Td¶ |
515-516 |
70.7
(66.5, 74.6) |
17.3
(14.1, 20.8) |
99.8
(98.9, 100.0) |
98.4
(97.0, 99.3) |
95.0
(92.7, 96.7) |
| 18-64 |
Adacel |
739-741 |
62.6
(59.0, 66.1) |
14.3
(11.9, 17.0) |
94.1‡
(92.1, 95.7) |
78.0§
(74.8, 80.9) |
87.4‡
(84.8, 89.7) |
| 18-64 |
Td¶ |
506-507 |
63.3
(59.0, 67.5) |
16.0
(12.9, 19.5) |
95.1
(92.8, 96.8) |
79.9
(76.1, 83.3) |
83.4
(79.9, 86.5) |
* N = number of participants in the per-protocol population with available data.
† Booster response is defined as: A 4-fold rise in antibody concentration, if the pre-vaccination concentration was equal to or below the cut-off value and a 2-fold rise in antibody concentration if the pre-vaccination concentration was above the cut-off value. The cut-off value for diphtheria was 2.56 IU/mL.
‡ Seroprotection rates at ≥0.10 IU/mL and booster response rates to Adacel were non-inferior to Td vaccine (upper limit of the 95% CI on the difference for Td vaccine minus Adacel <10%).
§ Seroprotection rates at ≥1.0 IU/mL were not prospectively defined as a primary endpoint.
¶ Tetanus and Diphtheria Toxoids Adsorbed manufactured by Sanofi Pasteur Inc., Swiftwater, PA. |
Table 6: Ratio of Pertussis Antibody Geometric Mean Concentrations (GMCs)* Observed One Month Following a First Vaccination with Adacel in Adolescents and Adults 11 through 64 Years of Age Compared with Those Observed in Infants One Month Following Vaccination at 2,4 and 6 Months of Age in the Efficacy Trial with DAPTACEL (Sweden I Efficacy Study)
|
Adolescents 11-17 Years of Age
Adacel†/DAPTACEL‡ GMC Ratio
(95% CIs) |
Adults 18-64 Years of Age
Adacel§/DAPTACEL‡ GMC Ratio
(95% CIs) |
| Anti-PT |
3.6
(2.8, 4.5)¶ |
2.1
(1.6, 2.7)¶ |
| Anti-FHA |
5.4
(4.5, 6.5)¶ |
4.8
(3.9, 5.9)¶ |
| Anti-PRN |
3.2
(2.5, 4.1)¶ |
3.2
(2.3, 4.4)¶ |
| Anti-FIM |
5.3
(3.9, 7.1)¶ |
2.5
(1.8, 3.5)¶ |
* Antibody GMCs, measured in arbitrary ELISA units were calculated separately for infants, adolescents and adults.
† N = 524 to 526, number of adolescents in the per-protocol population with available data for Adacel.
‡ N = 80, number of infants who received DAPTACEL with available data post dose 3 (Sweden Efficacy I).
§ N = 741, number of adults in the per-protocol population with available data for Adacel.
¶ GMC following Adacel was non-inferior to GMC following DAPTACEL (lower limit of 95% CI on the ratio of GMC for Adacel divided by DAPTACEL >0.67). |
Table 7: Booster Response Rates to the Pertussis Antigens Observed One Month Following a First Vaccination with Adacel in Adolescents and Adults 11 through 64 Years of Age
|
Adolescents 11-17 Years of Age N‡ |
Adolescents 11-17 Years of Age %
(95% CI) |
Adults 18-64 Years of Age N‡ |
Adults 18-64 Years of Age %
(95% CI) |
Predefined Acceptable Rates* %† |
| Anti-PT |
524 |
92.0
(89.3, 94.2) |
739 |
84.4
(81.6, 87.0) |
81.2 |
| Anti-FHA |
526 |
85.6
(82.3, 88.4) |
739 |
82.7
(79.8, 85.3) |
77.6 |
| Anti-PRN |
525 |
94.5
(92.2, 96.3) |
739 |
93.8
(91.8, 95.4) |
86.4 |
| Anti-FIM |
526 |
94.9
(92.6, 96.6) |
739 |
85.9
(83.2, 88.4) |
82.4 |
* The acceptable response rate for each antigen was defined as the lower limit of the 95% CI for the rate being no more than 10% lower than the response rate observed in previous clinical trials.
† A booster response for each antigen was defined as a 4-fold rise in antibody concentration if the pre-vaccination concentration was equal to or below the cut-off value and a 2-fold rise in antibody concentration if the pre-vaccination concentration was above the cut-off value. The cut-off values for pertussis antigens were established based on antibody data from both adolescents and adults in previous clinical trials. The cut-off values were 85 EU/mL for PT, 170 EU/mL for FHA, 115 EU/mL for PRN and 285 EU/mL for FIM.
‡ N = number of participants in the per-protocol population with available data. |
Study NCT01311557 assessed the comparative immunogenicity of a first vaccination with Adacel administered to adolescents (10 to <11 years of age and 11 to <12 years of age) [see ADVERSE REACTIONS] In this study non-inferiority was demonstrated for booster responses to tetanus and diphtheria toxoids, GMCs to the pertussis antigens (PT, FHA, PRN and FIM) and booster responses to the pertussis antigens PT, FHA and PRN. For FIM, non-inferiority was not demonstrated as the lower bound of the 95% CI of the difference in booster response rates (-5.96%) did not meet the predefined criterion (>-5% when the booster response in the older age group was >95%).
Immunological Evaluation In Adults, 18 Through 64 Years Of Age Following A Second Vaccination With Adacel
In study NCT01439165 [see ADVERSE REACTIONS], subjects 18 to 64 years of age who had received a dose of Adacel 8-12 years previously, were randomized to receive a second dose of Adacel or Td vaccine (Tetanus and Diphtheria Toxoids Adsorbed manufactured by Sanofi Pasteur, Limited). Blood samples for immunogenicity analyses were obtained from participants pre-vaccination and approximately 28 days post-vaccination. The per-protocol analysis set was used for all immunogenicity analyses, and included 948 participants in the Adacel group and 317 participants in the Td control vaccine group. Of the study participants, 35% were male. Of subjects who reported a racial/ethnic demographic, 95% were Caucasian, 2% Black, 0.5% American Indian or Alaska native, 1% Asian and 1.5% were of mixed or other origin.
A tetanus antitoxoid level of ≥0.1 IU/mL, measured by the ELISA used in this study was considered protective. An anti-diphtheria anti-toxin level of ≥0.1 IU/mL was considered protective. Pre-vaccination and post-vaccination seroprotection rates and booster response rates are presented in Table 8.
Table 8: Pre-vaccination and Post-vaccination Seroprotection Rates and Booster Response Rates to Tetanus Toxoid and Diphtheria Toxoid Following a Second Vaccination with Adacel Compared to Td Vaccine in Persons 18 through 64 Years of Age, Per Protocol Analysis Set
|
Vaccine |
N* |
Pre-vaccination ≥0.1 IU/mL (95% CI) |
Pre-vaccination ≥1.0I U/mL (95% CI) |
1 month post-vaccination ≥0.1 IU/mL (95% CI)† |
1 month post-vaccination ≥1.0 IU/mL (95% CI)‡ |
1 month post-vaccination %Booster§ (95% CI) |
| Anti- Tetanus Toxoid (ELISA - IU/mL) |
Adacel |
944-948 |
97.2
(96.0; 98.2) |
62.3
(59.1; 65.4) |
100.0
(99.6; 100.0) |
99.9
(99.4; 100.0) |
74.5¶#
(71.6; 77.2) |
| Anti- Tetanus Toxoid (ELISA - IU/mL) |
TdÞ Adsorbed |
315-317 |
96.5
(93.8; 98.2) |
63.8
(58.2; 69.1) |
100.0
(98.8; 100.0) |
100.0
(98.8; 100.0) |
81.6¶#
(76.9; 85.7) |
Anti-
Diphtheria
Toxin
(ELISA - IU/mL) |
Adacel |
945-948 |
84.7
(82.2; 86.9) |
29.1
(26.2; 32.1) |
99.8
(99.2; 100.0) |
94.9
(93.3; 96.2) |
83.2¶
(80.6; 85.5) |
Anti-
Diphtheria
Toxin
(ELISA - IU/mL) |
TdÞ Adsorbed |
315-317 |
83.8
(79.3; 87.7) |
29.8
(24.8; 35.2) |
99.4
(97.7; 99.9) |
94.0
(90.8; 96.4) |
84.1¶
(79.6; 88.0) |
* N = number of participants in the per-protocol population with available data.
† Seroprotection rates at ≥0.10 IU/mL for Adacel were non-inferior to Td for diphtheria toxin and tetanus toxoid (upper limit of the 95% CI on the difference for Td vaccine minus Adacel <10%).
‡ Seroprotection rates at ≥1.0 IU/mL were not prospectively defined as a primary or secondary endpoint.
§ Booster response is defined as a minimum rise in antibody concentration from pre to post-vaccination. The minimum rise is at least 2 times if the pre-vaccination concentration is above the cutoff value, or at least 4 times if it is at or below the cutoff value. The cutoff values for to tetanus and diphtheria are 2.7 IU/mL and 2.56 IU/mL, respectively.
¶ n/M: defines the number n of participants with booster response / the number M of subjects with available data to evaluate booster response. There were (n/M) 703/944, 257/315, 786/945 and 265/315 for Adacel/Tetanus, Td Adsorbed/Tetanus, Adacel/Diphtheria, and Td Adsorbed/Diphtheria, respectively.
# Booster response rates for tetanus toxoid in Adacel did not meet the pre-specified non-inferiority criteria.
Þ Tetanus and Diphtheria Toxoids Adsorbed manufactured by Sanofi Pasteur Limited, Toronto, Ontario, Canada. |
For all pertussis antigens (PT, FHA, PRN and FIM), post-vaccination anti-pertussis GMCs in the Adacel group were non-inferior to GMCs induced by 3 or 4 doses of DAPTACEL in historical studies as are presented in Table 9.
Table 9: Ratio of Pertussis Antibody Geometric Mean Concentrations (GMCs) Observed One Month Following a Second Vaccination with Adacel in Adults Compared with Those Observed in Infants One Month following Vaccination with 3 or 4 Doses of DAPTACEL (Per-Protocol Analysis Set)
| Antigen |
N |
Adacel
GMC
(EU/mL) |
Adacel
(95% CI) |
N |
DAPTACEL*
GMC
(EU/mL) |
DAPTACEL*
(95% CI) |
Adacel
/DAPTACEL*
GMC Ratio |
(95%CI)† |
| PT |
935 |
102 |
(94.9; 110) |
366 |
98.1 |
(90.9; 106) |
1.04 |
(0.92; 1.18) |
| FHA |
948 |
209 |
(200; 217) |
80 |
39.9 |
(34.6; 46.1) |
5.22 |
(4.51; 6.05) |
| PRN |
948 |
318 |
(302; 334) |
80 |
108 |
(91.4; 128) |
2.94 |
(2.46; 3.51) |
| FIM |
948 |
745 |
(711; 781) |
80 |
341 |
(270; 431) |
2.18 |
(1.84; 2.60) |
* DAPTACEL: Historical controls who received DAPTACEL in Sanofi Pasteur studies. PT antibody GMC were compared to GMC following 4 doses of DAPTACEL in NCT00255047. FHA, PRN and FIM antibody GMCs were compared to GMCs following 3 doses of Daptacel in the Sweden I Efficacy trial.
† For each pertussis antigen, non-inferiority was demonstrated if the lower limit of the 2-sided 95% CI of the GMC ratio (Adacel divided by the historical control) was > 0.66. |
Booster response rates for PT and FHA were non-inferior in Adacel participants compared to pre-specified criteria for booster response rates, but non-inferiority was not achieved for PRN and FIM booster response rates (See Table 10).
Table 1: Comparison of Booster Response* Rates for Pertussis Antigens Following a Second Vaccination with Adacel (Per-Protocol Analysis Set)
|
Adacel
(N=948) |
Adacel
(N=948) |
Pre-specified criteria for Booster Response Rates† |
Adacel minus Pre-specified Booster Response Rates† |
Adacel minus Pre-specified Booster Response Rates† |
| Antigen |
n/M |
% (95% CI) |
% |
Difference (%) |
(95% CI)‡ |
| PT |
693/894 |
77.5
(74.6;
80.2) |
61.4 |
16.12 |
(13.27;18.73) |
| FHA |
651/945 |
68.9
(65.8; 71.8) |
73.1 |
-4.21 |
(-7.23; -1.34) |
| PRN |
617/945 |
65.3
(62.2; 68.3) |
83.9 |
-18.61 |
(-21.7; -15.6) |
| FIM |
537/945 |
56.8
(53.6; 60.0) |
75.9 |
-19.07 |
(-22.3; -16.0) |
N = number of subjects analyzed according to Per-Protocol Analysis Set
M = number of subjects with available data for the considered endpoint
n = number of subjects fulfilling the item listed in the first column
* Booster response is defined as a minimum rise in antibody concentration from pre to post-vaccination. The minimum rise is at least 2-fold if the pre-vaccination concentration is above the cutoff value, or at least 4-fold if it is at or below the cutoff value. The cutoff values for Study NCT01439165 for the pertussis antigens are: 93 EU/mL for PT, 170 EU/mL for FHA, 115 EU/mL for PRN, and 285 EU/mL for FIM.
† Pre-specified criteria for booster response rates were derived from participants 21 to <65 years of age who received Adacel in Study Td506.
‡ Non-inferiority in booster response rate for each pertussis antigen was demonstrated if the lower limit of the 2-sided 95% CI of the difference of booster response rates between participants receiving Adacel in Study NCT01439165 and expected booster response rates based on Study Td506 was >-10%. |
Study In Pregnant Women
The effectiveness of Adacel immunization during the third trimester of pregnancy to prevent pertussis among infants younger than 2 months of age was assessed based on a re-analysis of the Adacel-relevant data (Study NCT05040802) from an observational study of Tdap vaccine effectiveness in the United States (9). This matched case-control study included pertussis cases reported from 2011 through 2014 in infants born at ≥ 37 weeks gestation and ≥ 2 days old. A case of pertussis was defined as the onset of cough illness and at least one of the following: laboratory-confirmation (culture or PCR) of pertussis, epidemiological linkage to a laboratory-confirmed case, or clinically-compatible illness (cough ≥2 weeks with paroxysms, inspiratory whoop or post-tussive vomiting) in an infant <2 months old. NCT05040802 included a total of 596 infants (179 cases of pertussis and 417 controls without pertussis), the mean age was 4.2 (SD, 2.5) weeks, and 45.7% were non-Hispanic. For the vaccine effectiveness re-analysis, a conditional logistic regression model controlling for infant’s age and maternal education, was fit to data from 101 cases (including 5 infants whose mothers received Adacel during the third trimester and ≥14 days before delivery) and 171 controls (including 27 infants whose mothers received Adacel during the third trimester and ≥14 days before delivery) matched by birth hospital. This resulted in a vaccine effectiveness estimate of 88.0% (95% CI: 43.8, 97.4) for vaccination during the third trimester and ≥14 days before delivery.
Immune Responses To Pertussis Vaccination In Infants Born To Mothers Who Received Adacel During Pregnancy
Published studies have reported diminished immune responses to pertussis antigens in DTaP-containing vaccines administered to infants whose mothers received Adacel during the third trimester of pregnancy compared with infants whose mothers did not receive Adacel during the third trimester of pregnancy (10, 11). Whether the diminished immune responses observed in vaccinated infants whose mothers received Adacel during pregnancy result in diminished effectiveness of pertussis vaccination in infants is unknown.
Concomitant Hepatitis B Vaccine Administration
The concomitant use of Adacel (first vaccination) and hepatitis B (Hep B) vaccine (Recombivax HB®, 10 mcg per dose using a two-dose regimen, manufactured by Merck and Co., Inc.) was evaluated in a multi-center, open-labeled, randomized, controlled study that enrolled 410 adolescents, 11 through 14 years of age inclusive. One group received Adacel and Hep B vaccines concurrently (N = 206). The other group (N = 204) received Adacel at the first visit, then 4-6 weeks later received Hep B vaccine. The second dose of Hep B vaccine was given 4-6 weeks after the first dose. Serum samples were obtained prior to and 4-6 weeks after Adacel administration, as well as 4-6 weeks after the 2nd dose of Hep B for all participants. No interference was observed in the immune responses to any of the vaccine antigens when Adacel and Hep B vaccines were given concurrently or separately. [see ADVERSE REACTIONS]
Concomitant Influenza Vaccine Administration
The concomitant use of Adacel (first vaccination) and trivalent inactivated influenza vaccine (TIV, Fluzone®, manufactured by Sanofi Pasteur Inc., Swiftwater, PA) was evaluated in a multi-center, open-labeled, randomized, controlled study conducted in 720 adults, 19-64 years of age inclusive. In one group, participants received Adacel and TIV vaccines concurrently (N = 359). The other group received TIV at the first visit, then 4-6 weeks later received Adacel (N = 361).
Sera were obtained prior to and 4-6 weeks after Adacel, as well as 4-6 weeks after the TIV. The immune responses were comparable for concurrent and separate administration of Adacel and TIV vaccines for diphtheria (percent of participants with seroprotective concentration ≥0.10 IU/mL and booster responses), tetanus (percent of participants with seroprotective concentration ≥0.10 IU/mL), pertussis antigens (booster responses and GMCs except lower PRN GMC in the concomitant group, lower bound of the 90% CI was 0.61 and the prespecified criterion was ≥0.67) and influenza antigens (percent of participants with hemagglutination-inhibition [HI] antibody titer ≥1:40 IU/mL and ≥4-fold rise in HI titer). Although tetanus booster response rates were significantly lower in the group receiving the vaccines concurrently versus separately, greater than 98% of participants in both groups achieved seroprotective levels of ≥0.1 IU/mL. [see ADVERSE REACTIONS]
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