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Pharmacotherapeutic group: Associated bacterial and viral vaccines. ATC code: J07CA06.
Pharmacology: Pharmacodynamics: The diphtheria and tetanus toxins are detoxified by formaldehyde, and then purified.
The poliomyelitis vaccine is obtained by culture of polio virus types 1, 2 and 3 on Vero cells, purified, and then inactivated by formaldehyde.
The acellular pertussis components (PT and FHA) are extracted from cultures of Bordetella pertussis, then purified. The pertussis toxin (PT) is detoxified by glutaraldehyde and corresponds to pertussis toxoid (PTxd). The FHA is native. PTxd and FHA have been shown to play a major role in protection as regards pertussis.
The capsular polysaccharide PRP (polyribosyl ribitol phosphate) is extracted from the culture of Haemophilus influenzae type b, and conjugated to the protein tetanus (T) constituting the PRP-T conjugate vaccine.
Capsular polysaccharide (polyribosyl ribitol phosphate: PRP) induces a serological anti-PRP response in humans. However, as with all polysaccharide antigens, the immune response is thymus-independent, characterised by low immunogenicity in infants, and by the absence of a booster effect before the age of 15 months. The covalent bond of the capsular polysaccharide of Haemophilus influenzae type b to a carrier protein, tetanus protein, allows the conjugate vaccine to behave as a thymus-dependent antigen leading to a specific anti-PRP serological response in the infant, and to achieve a booster effect.
Immune response after primary vaccination: Immunogenicity studies performed in infants one month after primary vaccination showed that all infants (100%) developed a protective antibody titre (>0.01 IU/mL) against diphtheria and tetanus antigens.
For pertussis, one month after receiving the three primary doses, anti-PT and anti-FHA antibody titres increased fourfold in 93%, and more than 88% of infants, respectively.
At least 99% of primary vaccinated children had protective titres of antibodies directed against poliomyelitis virus types 1, 2, and 3 (≥5 reciprocal of dilution in seroneutralisation).
Finally, one month after the third dose of primary vaccination, at least 97.2% of vaccinated infants have an anti-PRP antibody titre greater than 0.15 μg/mL.
Immune response after booster: After the first booster dose (16-18 months), all the children developed protective antibody titres against diphtheria (>0.1 IU/mL) and tetanus (>0.1 IU/mL), and against poliomyelitis viruses (≥5 reciprocal of dilution in seroneutralisation).
The rate of seroconversion to pertussis antibodies (titres greater than 4 times the pre-vaccination titres) is at least 98% for PT (EIA) and 99% for FHA (EIA).
An anti-PRP antibody titre of ≥1.0 μg/mL was obtained in all children.
A follow-up study of pertussis immunogenicity in children aged 5-6 years showed that the anti-PT and anti-FHA antibody titres of children who received primary and booster vaccinations with combined acellular vaccines were at least equivalent to those observed in children of the same age who had been vaccinated with combined whole-cell pertussis vaccines.
Pharmacokinetics: Not applicable.
Toxicology: Preclinical Safety Data: Non-clinical data reveal no special hazard for humans based on conventional studies of acute toxicity, repeated dose toxicity and local tolerability.
