CLINICAL PHARMACOLOGY
Mechanism Of Action
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 ≥0.1 IU/mL are generally regarded as
protective. (6) Levels of 1.0 IU/mL have been associated with long-term
protection. (7)
Tetanus
Tetanus is an acute disease caused by an extremely potent
neurotoxin produced by C. tetani. Protection against disease is due to
the development of neutralizing antibodies to tetanus toxin. A serum tetanus
antitoxin level of ≥0.01 IU/mL, measured by neutralization assay is
considered the minimum protective level. (6) (8) A tetanus antitoxoid level
≥0.1 IU/mL as measured by the ELISA used in clinical studies of VAXELIS
is considered protective.
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.
Poliomyelitis
Polioviruses, of which there are 3 serotypes (Types 1, 2,
and 3), are enteroviruses. The presence of poliovirus type-specific
neutralizing antibodies has been correlated with protection against
poliomyelitis. (9)
Hepatitis B
Hepatitis B virus is one of several hepatitis viruses
that cause systemic infection, with major pathology in the liver. Antibody
concentrations of ≥10 mIU/mL against HBsAg correlate with protection
against hepatitis B virus infection.
Haemophilus Influenzae Type b Invasive Disease
H. influenzae type b can cause invasive disease
such as meningitis and sepsis. Anti-PRP antibody has been shown to correlate
with protection against invasive disease due to H. influenzae type b.
Based on data from passive antibody studies (10) and an
efficacy study with H. influenzae type b polysaccharide vaccine in
Finland, (11) a post-vaccination anti-PRP level of ≥0.15 mcg/mL is
considered a minimal protective level. Data from an efficacy study with H.
influenzae type b polysaccharide vaccine in Finland indicate that an
anti-PRP level of ≥1.0 mcg/mL 3 weeks after vaccination predicts
protection through a subsequent 1-year period. (11) (12) These levels have been
used to evaluate the effectiveness of H. influenzae type b conjugate
vaccines, including the PRP-OMPC component of VAXELIS.
Clinical Studies
Effectiveness Of VAXELIS
The effectiveness of VAXELIS is based on the
immunogenicity of the individual antigens compared to US licensed vaccines.
Serological correlates of protection exist for diphtheria, tetanus, hepatitis
B, poliomyelitis, and invasive disease due to H. influenzae type b. The
effectiveness against pertussis is based upon the pertussis immune responses
following 3 doses of VAXELIS compared to 3 doses of Pentacel, as well as the
pertussis immune responses following a subsequent dose of DAPTACEL in the same
2 groups of children. VAXELIS, Pentacel and DAPTACEL contain the same pertussis
antigens, manufactured by the same processes.
Immunogenicity
In the US Study 005 (Table 1), infants were randomized to
receive 3 doses of VAXELIS at 2, 4, and 6 months of age and DAPTACEL and
PedvaxHIB at 15 months of age, or Control group vaccines (3 doses of Pentacel
vaccine at 2, 4, and 6 months of age + RECOMBIVAX HB at 2 and 6 months of age
and DAPTACEL and ActHIB at 15 months of age). All subjects received concomitant
vaccines: RotaTeq at 2, 4 and 6 months and Prevnar 13 at 2, 4, 6, and 15 months
of age. [See ADVERSE REACTIONS] All infants had received a dose of
hepatitis B vaccine prior to study initiation, prior to or at one month of age.
Among all randomized participants, 53.0% were male and 47.0% were female. Most
(79.2%) participants were White, 14.1% were Black and 5.2% were multi-racial.
Most (91.4%) participants were of non-Hispanic or non-Latin ethnicity.
Antibody responses to diphtheria, tetanus, pertussis (PT,
FHA, PRN and FIM), poliovirus types 1, 2 and 3, hepatitis B and H.
influenzae type b antigens were measured in sera obtained one month
following the third dose of VAXELIS or Pentacel + RECOMBIVAX HB vaccines.
VAXELIS was non-inferior to Pentacel + RECOMBIVAX HB administered concomitantly
at separate sites, as demonstrated by the proportions of participants achieving
seroprotective levels of antibodies to diphtheria, tetanus, poliovirus,
hepatitis B and PRP antigens, and pertussis vaccine response rates and GMCs
(except FHA), following 3 doses of the vaccine. See Table 3.
To complete the 4-dose pertussis primary vaccination
series, participants in both groups received DAPTACEL at 15 months of age and
were evaluated for immune responses to pertussis antigens one month later. The
non-inferiority criteria for vaccine response rates and GMCs for all pertussis
antigens were met following the fourth dose.
Table 3: Antibody Responses One Month Following Dose 3
of VAXELIS or Control Vaccines Administered Concomitantly with Prevnar 13 and
RotaTeq in Study 005
|
VAXELIS + Prevnar 13 + RotaTeq
(N=688 - 810) |
Pentacel + RECOMBIVAX HB + Prevnar 13 + RotaTeq
(N=353 - 400) |
Anti-Diphtheria Toxoid |
% ≥0.1 IU/mL |
82.4* |
86.3 |
Anti-Tetanus Toxoid |
% ≥0.1 IU/mL |
99.9† |
99.5 |
Anti-PT |
% vaccine response‡ |
98.1* |
98.5 |
GMC |
109.6§ |
85.4 |
Anti-FHA |
% vaccine response‡ |
87.3* |
92.0 |
GMC |
46.6¶ |
72.3 |
Anti-PRN % |
vaccine response‡ |
79.3* |
82.0 |
GMC |
55.8§ |
66.8 |
Anti-FIM |
% vaccine response‡ |
90.2* |
86.2 |
GMC |
235.9§ |
184.4 |
Anti-Poliovirus Type 1 |
% ≥1:8 dilution |
100.0† |
98.2 |
Anti-Poliovirus Type 2 |
% ≥1:8 dilution |
100.0† |
99.7 |
Anti-Poliovirus Type 3 |
% ≥1:8 dilution |
100.0† |
99.8 |
Anti-PRP |
% ≥0.15 μg/mL |
97.3† |
92.4 |
% ≥1.0 μg/mL |
85.0* |
75.3 |
Anti-HBsAg |
% ≥10 mIU/mL |
99.4* |
98.6 |
N= The number of participants with available data.
* Non-inferiority criterion met (lower bound of 2-sided 95% CI for the
difference [VAXELIS group minus Control vaccines group] was >-10%).
† Non-inferiority criterion met (lower bound of 2-sided 95% CI for the
difference [VAXELIS group minus Control vaccines group] was >-5%).
‡ Vaccine response = if pre-vaccination antibody concentration was <4 x
lower limit of quantitation [LLOQ], then the post-vaccination antibody
concentration was ≥4 x LLOQ; if pre-vaccination antibody concentration
was ≥4 x LLOQ, then the post-vaccination antibody concentration was
≥pre-vaccination levels (pre-Dose 1).
§ Non-inferiority criterion met (lower bound of 2-sided 95% CI for the GMC
ratio [VAXELIS group/Control vaccines group] was >0.67).
¶ Non-inferiority criterion not met for anti-FHA GMC (lower bound of 2-sided
95% CI for the GMC ratio [VAXELIS group/Control vaccines group was 0.59 which is
below the non-inferiority criterion >0.67). |
Study 006 (Table 1) was a lot consistency study conducted
in the US, where infants were randomized to receive 3 doses of VAXELIS at 2, 4,
and 6 months of age and Pentacel at 15 months of age (N=2,406), or control
group vaccines (4 doses of Pentacel at 2, 4, 6, and 15 months of age +
RECOMBIVAX HB at 2 and 6 months of age; N=402). All subjects received
concomitant vaccines: RotaTeq at 2, 4 and 6 months and Prevnar 13 at 2, 4, 6,
and 15 months of age. All infants had received a dose of hepatitis B vaccine
prior to study initiation, from birth up to one month of age.
Antibody responses to diphtheria, tetanus, pertussis (PT,
FHA, PRN and FIM), poliovirus types 1, 2 and 3, hepatitis B and H.
influenzae type b antigens were measured in sera obtained one month
following the third dose of VAXELIS or Pentacel + RECOMBIVAX HB. VAXELIS was
non-inferior to Pentacel + RECOMBIVAX HB administered concomitantly at separate
sites, as demonstrated by the proportions of participants achieving
seroprotective levels of antibodies to diphtheria, tetanus, poliovirus,
hepatitis B and PRP antigens, and pertussis vaccine response rates and GMCs,
except for GMCs for FHA (lower bound of 2-sided 95% CI for GMC ratio [VAXELIS
group/Control group vaccines] was 0.62, which was below the non-inferiority
criterion >0.67).
To complete the 4-dose pertussis primary vaccination
series, participants in both groups received Pentacel at 15 months of age and
were evaluated for immune responses to pertussis antigens one month later. The
non-inferiority criteria for antibody vaccine response rates and GMCs for all
pertussis antigens were met following the fourth dose except for GMCs for PRN
(lower bound of 2-sided 95% CI for GMC ratio [VAXELIS group/Control group
vaccines] was 0.66, which was below the non-inferiority criterion >0.67).
Concomitantly Administered Vaccines
In Study 006 conducted in the US (Table 1), the immune
responses to Prevnar 13 were measured one month after the third dose.
Non-inferiority criteria were met for GMCs to 12 of the 13 serotype antigens in
Prevnar 13 for participants who received VAXELIS relative to Control vaccines.
For serotype 6B, the non-inferiority criterion was not met (lower bound of 2-sided
95% CI for GMC ratio [VAXELIS group/Control vaccines group] is 0.64, which is
below the non-inferiority criterion >0.67). 16
REFERENCES
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SA, Orenstein WA, and Offit PA, editors. Vaccines. 6th ed. Philadelphia, PA: WB
Saunders; 2013:153-66.
8 Roper M, Wassilak SGF, Tiwari TSP, Orenstein WA.
Tetanus toxoid. In: Plotkin SA, Orenstein WA, Offit PA, editors. Vaccines. 6th
ed. Philadelphia, PA: WB Saunders; 2013. p. 746-72.
9 Sutter RW, et al. Defining surrogate serologic tests
with respect to predicting protective vaccine efficacy: Poliovirus vaccination.
In: Williams JC, et al. eds. Combined vaccines and simultaneous administration.
Current issues and perspectives. New York, NY: The New York Academy of
Sciences. 1995:289-99.
10 Robbins, J. B., et al: Quantitative measurement of
'natural' and immunization-induced Haemophilus influenzae type b capsular
polysaccharide antibodies. Pediatr Res 1973;7(3):103-10.
11 Kayhty H, et al. The protective level of serum
antibodies to the capsular polysaccharide of Haemophilus influenzae type b. J
Infect Dis 1983;147:1100.
12 Anderson P. The protective level of serum antibodies
to the capsular polysaccharide of Haemophilus influenzae type b. J Infect Dis
1984;149:1034. 17