Infanrix (Diphtheria and Tetanus Toxoids and Acellular Pertussis Vaccine Adsorbed) is a sterile combination of diphtheria and tetanus toxoids and three pertussis antigens [inactivated pertussis toxin (PT), filamentous hemagglutinin (FHA) and pertactin (69 kiloDalton outer membrane protein)] adsorbed onto aluminum hydroxide. Infanrix is intended for intramuscular injection only. After shaking, the vaccine is a homogeneous white turbid suspension.

Three acellular pertussis antigens (pertussis toxin [PT], filamentous hemagglutinin [FHA] and pertactin) are isolated from phase 1 Bordetella pertussis culture grown in modified Stainer-Scholte liquid medium. PT and FHA are extracted from the fermentation broth by adsorption on hydroxyapatite gel; pertactin is extracted from the cells by heat treatment and flocculation using barium chloride. These antigens are purified in successive chromatographic steps: PT and FHA by hydrophobic, affinity and size exclusion; pertactin by ion exchange, hydrophobic and size exclusion processes. PT is detoxified using formaldehyde and glutaraldehyde. FHA and pertactin are treated with formaldehyde.

Diphtheria toxin is produced by growing Corynebacterium diphtheriae in Linggoud and Fenton medium containing a bovine extract. Tetanus toxin is produced by growing Clostridium tetani in a modified Latham medium. Both toxins are detoxified with formaldehyde, concentrated by ultrafiltration, and purified by precipitation, sterile filtration and dialysis.

Each antigen is individually adsorbed onto aluminum hydroxide. Each 0.5 mL dose contains, by assay, not more than 0.625 mg aluminum. Each 0.5 mL dose is formulated to contain 25 Lf diphtheria toxoid, 10 Lf tetanus toxoid (both toxoids induce at least 2 antitoxin units/mL of serum in the guinea pig potency test), 25 mcg PT, 25 mcg FHA and 8 mcg pertactin. The potency of the pertussis component is evaluated by measurement of the antibody response to PT, FHA and pertactin in immunized mice using an ELISA.

Each 0.5 mL dose also contains 2.5 mg 2-phenoxyethanol as a preservative, 4.5 mg sodium chloride, water for injection and not more than 0.02% (w/v) residual formaldehyde. The vaccine contains polysorbate 80 (Tween 80) which is used in the production of the pertussis concentrate. The inactivated acellular pertussis components contribute less than 5 endotoxin units (EU) per 0.5 mL dose.

Diphtheria and Tetanus Toxoids adsorbed bulk concentrates for further manufacturing use are produced by Chiron Behring GmbH & Co, Marburg, Germany. The acellular pertussis antigens are manufactured by SmithKline Beecham Biologicals S.A., Rixensart, Belgium. Formulation, filling, testing, packaging and release of the vaccine are conducted by SmithKline Beecham Biologicals S.A.

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