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Pharmacology: Pharmacodynamics: Immune response: Approximately one month following booster vaccination with Boostrix, the following seroprotection/seropositivity rates were observed: See Table 1.
Click on icon to see table/diagram/imageIn adolescents and adults, comparative trials have demonstrated that one month post-vaccination, diphtheria antibody titres are similar to adult-type Td vaccines with the same antigen content as Boostrix; lower tetanus antibody titres were seen as compared to adult-type Td vaccines.
As with other adult-type Td vaccines, Boostrix induces higher titres of both anti-D and anti-T antibodies in children and adolescents as compared to adults.
Persistence of the immune response: Three to 3.5 years, 5 to 6 years and 10 years following a first vaccination with Boostrix, the following seroprotection/seropositivity rates were observed in subjects vaccinated according to protocol (ATP) (Table 2): See Table 2.
Click on icon to see table/diagram/imageEfficacy in protecting against pertussis: The pertussis antigens contained in Boostrix are an integral part of the paediatric acellular pertussis combination vaccine (Infanrix), for which efficacy after primary vaccination has been demonstrated in a household contact efficacy study. The antibody titres to all three pertussis components following vaccination with Boostrix are higher than those observed during the household contact efficacy trial. Based on these comparisons, Boostrix would provide protection against pertussis, however the degree and duration of protection afforded by the vaccine are undetermined.
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 (dTpa group; N=291) versus placebo (control group; N=292) at 27-36 weeks of pregnancy. The cord blood geometric mean concentrations of antibodies against the pertussis antigens PT, FHA and PRN were 46.9, 366.1, and 301.8 IU/ml in the dTpa group, and 5.5, 22.7, and 14.6 IU/ml in the control group. This corresponds to antibody titres that are 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: The immunogenicity of Infanrix hexa (diphtheria, tetanus, pertussis, hepatitis B, inactivated poliovirus, Haemophilus influenzae type b conjugate vaccine) in infants and toddlers born to healthy mothers vaccinated with Boostrix at 27-36 weeks of pregnancy was evaluated in two clinical studies.
Infanrix hexa was co-administered with a 13-valent pneumococcal conjugate vaccine to infants for primary vaccination (n=268); and to the same infants/toddlers from 11 to 18 months as booster dose (n=229).
Post-primary and post-booster vaccination, immunological data did not show clinically relevant interference of maternal vaccination with Boostrix on the infant's and toddler's responses to diphtheria, tetanus, hepatitis B, inactivated poliovirus, Haemophilus influenzae type b or pneumococcal antigens.
Lower antibody concentrations against pertussis antigens post-primary (PT, FHA and PRN) and post-booster (PT, FHA) vaccination were observed in infants and toddlers born to mothers vaccinated with Boostrix during pregnancy. The fold-increases of anti-pertussis antibody concentrations from the pre-booster to the 1-month post-booster time point were in the same range for infants and toddlers born to mothers vaccinated with Boostrix or with placebo, demonstrating effective priming of the immune system. In the absence of correlates of protection for pertussis, the clinical relevance of these observations remains to be fully understood. However, current epidemiological data on pertussis disease following the implementation of dTpa maternal immunisation 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 following table. (See Table 3.)
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.
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: After administration of one dose of Boostrix to 83 adolescents aged from 11 to 18 years, without previous pertussis vaccination and no vaccination against diphtheria and tetanus in the previous 5 years, all subjects were seroprotected against tetanus and diphtheria. The seropositivity rate after one dose varied between 87% and 100% for the different pertussis antigens.
After administration of one dose of Boostrix to 139 adults ≥40 years of age that had not received any diphtheria and tetanus containing vaccine in the past 20 years, more than 98.5% of adults were seropositive for all three pertussis antigens and 81.5% and 93.4% were seroprotected against diphtheria and tetanus respectively. After administration of two additional doses one and six months after the first dose, the seropositivity rate was 100% for all three pertussis antigens and the seroprotection rates for diphtheria and tetanus reached 99.3% and 100% respectively.
Pharmacokinetics: Evaluation of pharmacokinetic properties is not required for vaccines.
Toxicology: Preclinical safety data: Reproductive toxicology: Fertility: Non-clinical data obtained with Boostrix reveal no specific hazard for humans based on conventional studies of female fertility in rats and rabbits.
Pregnancy: Non-clinical data obtained with Boostrix reveal no specific hazard for humans based on conventional studies of embryo-foetal development in rats and rabbits, and also of parturition and postnatal toxicity in rats (up to the end of the lactation period).
Animal toxicology and/or pharmacology: Preclinical data reveal no special hazard for humans based on conventional studies of safety and of toxicity.
