Infanrix-IPV Mechanism of Action

Pharmacotherapeutic Group: Combined bacterial and viral vaccines. ATC Code: J07CA02.
Pharmacology: Pharmacodynamics: Immune response to the DT components: One month after a primary vaccination course, more than 99% of infants vaccinated with Infanrix-IPV had antibody titres of ≥ 0.1 IU/ml to both tetanus and diphtheria.
Following administration of a booster dose of Infanrix-IPV, more than 99.5% of children had antibody titres of ≥ 0.1 IU/ml for both antigens.
Immune response to the Pa component: One month after the 3-dose primary vaccination course with Infanrix-IPV, 100% of infants were seropositive for the three pertussis components (PT, FHA, pertactin), and the overall response rates for each of the three individual pertussis antigens were ≥ 94%.
A booster response was seen in the vast majority of vaccinees against the pertussis antigens; lower response rates were seen in studies where the pre-vaccination levels of antibodies were high. All subjects were seropositive 1 month after this dose.
Protective efficacy of the Pa component: As the immune response to pertussis antigens following Infanrix-IPV administration is equivalent to that of Infanrix, it can be assumed that the protective efficacy of the two vaccines will also be equivalent.
The clinical protection of the DTPa component, against WHO-defined typical pertussis (≥ 21 days of paroxysmal cough) was demonstrated in: 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%; a NIH sponsored efficacy study performed in Italy (2, 4, 6 months schedule), the vaccine efficacy was found to be 84%. In a follow-up of the same cohort, the efficacy was confirmed for up to 4 years of age.
Immune response to the IPV component: One month after the primary vaccination, the overall seropositivity for each of the three serotypes (type 1, 2 and 3) was ≥ 99.5%.
Following administration of a booster dose of Infanrix-IPV, 100% of children were seropositive for the three serotypes.
In all booster trials, vaccination induced a marked increase in antibody levels with respect to pre-booster values.
Pharmacokinetics: Evaluation of pharmacokinetic properties is not required for vaccines.