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Pharmacology: Pharmacodynamics: Immune response: Approximately one month following booster vaccination with Boostrix: seropositivity/seroprotection rate against the different vaccine components was at least 99% in children from 4 to 9 years of age.
Seropositivity/seroprotection rate against the different vaccine components was at least 97% in adults and adolescents from 10 years of age.
Results of the comparative studies with commercial dT vaccines indicates that the degree and duration of protection would not be different from those obtained with these vaccines.
Efficacy in protecting against pertussis: There is currently no correlate of protection defined for pertussis; however, the protective efficacy of GlaxoSmithKline Biologicals' DTPa (Infanrix) vaccine against WHO-defined typical pertussis (≥21 days of paroxysmal cough with laboratory confirmation) was demonstrated in the following 3-dose primary studies: a prospective blinded household contact study performed in Germany (3, 4, 5 months schedule). Based on data collected from secondary contacts in households where there was an index case with typical pertussis, the protective efficacy of the vaccine was 88.7%. Protection against laboratory confirmed mild disease, defined as 14 days or more of cough of any type was 73% and 67% when defined as 7 days or more of cough of any type.
An NIH sponsored efficacy study performed in Italy (2, 4, 6 months schedule). The vaccine efficacy was found to be 84%. When the definition of pertussis was expanded to include clinically milder cases with respect to type and duration of cough, the efficacy of Infanrix was calculated to be 71% against >7 days of any cough and 73% against >14 days of any cough.
Vaccinees receiving Boostrix achieved antipertussis antibody titres greater than those in the German household contact study where the protective efficacy was 88.7%.
Passive protection against pertussis in infants (below 3 months of age) born to mothers vaccinated during pregnancy: In a randomised, cross-over, placebo-controlled study, higher pertussis antibody concentrations were demonstrated at delivery in the cord blood of babies born to mothers vaccinated with Boostrix (N=291) versus placebo (N=292) between 27 and 36 weeks of pregnancy. The concentrations of antibodies against the pertussis antigens PT, FHA and PRN were respectively 8, 16 and 21 times higher in the cord blood of babies born to vaccinated mothers versus controls. These antibody titres may provide passive protection against pertussis, as shown by observational effectiveness studies.
Immunogenicity in infants and toddlers born to mothers vaccinated during pregnancy: In follow-up trials in the infants following primary vaccination (n=268) and subsequently following booster vaccination in the same toddlers (n=229) born to the vaccinated mothers, the clinical data did not show clinically relevant interference between maternal vaccination with Boostrix and the infant and toddler response to diphtheria, tetanus, hepatitis B, inactivated polio virus, Haemophilus influenzae type b or pneumococcal antigens. Although lower concentrations of antibodies against some pertussis antigens were observed post-primary and post-booster vaccination in infants born to vaccinated mothers (as compared to infants born to unvaccinated mothers), 92.1-98.1% of the subjects born to vaccinated mothers showed a booster response against all pertussis antigens. Current epidemiological data on pertussis disease do not suggest any clinical relevance of this immune interference.
Effectiveness in the protection against pertussis disease in infants born to women vaccinated during pregnancy: Boostrix or Boostrix Polio vaccine effectiveness (VE) was evaluated in three observational studies, in UK, Spain and Australia. The vaccine was used during the third trimester of pregnancy to protect infants below 3 months of age against pertussis disease, as part of a maternal vaccination programme.
Details of each study design and results are provided in the table as follows.
VE against pertussis disease for infants below 3 months of age born to mothers vaccinated during the third trimester of pregnancy with Boostrix/Boostrix Polio (see table):
Click on icon to see table/diagram/imageIf maternal vaccination occurs within two weeks before delivery, vaccine effectiveness in the infant may be lower than the figures in the table.
Persistence of immune system: Five to 6 years following vaccination with Boostrix, at least 94% of children from the age of 4 years onwards were seroprotected or seropositive against all vaccine components, except for the pertussis toxoid component (52% of subjects were seropositive against pertussis toxoid).
Ten years following vaccination with Boostrix, at least 86% of adults were seroprotected or seropositive against all vaccine components.
In adolescents, the percentage of subjects who were seroprotected or seropositive was at least 82% against all vaccine components, except for the pertussis toxoid component (61% of subjects were seropositive against pertussis toxoid).
Immune response after a repeat dose of Boostrix: The immunogenicity of Boostrix, administered 10 years after a previous booster dose with reduced-antigen content diphtheria, tetanus and acellular pertussis vaccine(s) has been evaluated. One month post vaccination, >99% of subjects were seroprotected against diphtheria and tetanus and seropositive against pertussis.
Immune response in subjects without prior or with unknown vaccination history: In adolescents aged from 11 to 18 years, without previous pertussis vaccination and no vaccination against diphtheria and tetanus in the previous 5 years, one dose of Boostrix induced an antibody response against pertussis and all subjects were protected against tetanus and diphtheria.
In subjects ≥40 years of age that had not received any diphtheria or tetanus containing vaccine in the past 20 years (including those who have never been vaccinated or whose vaccination status was unknown), one dose of Boostrix induced an antibody response against pertussis and protected against tetanus and diphtheria in the majority of cases.
Toxicology: Pre-clinical Safety Data: Animal toxicology and/or pharmacology: Pre-clinical data reveal no special hazard for humans based on conventional studies of safety and of toxicity.
