Table II.
List of available typhoid vaccines
| Characteristics | Parenteral killed whole cell vaccine | Live attenuated Ty21a | Vi capsular polysaccharide | Conjugated typhoid vaccine |
|---|---|---|---|---|
| Constituent | Whole cell vaccine made from a non-motile mutant of S. Typhi strain Ty2 | Chemically mutated Ty2 strain of S. Typhi | Purified Vi capsular polysaccharide of the Ty2 S. Typhi strain | Vi polysaccharide attached to a non-toxic recombinant protein which is antigenically similar to rEPA |
| Vaccine type | Whole cell, killed | Live attenuated | Subunit | Subunit |
| Immunogenic properties | Stimulate the synthesis of 0, H and Vi antibodies | Induces mucosal IgA and serum IgG antibodies against O, H and other antigens, also cell-mediated responses Not shown any booster effect | Elicits serum IgG Vi antibodies T cell-independent (no booster response) | T cell-dependent response Booster response seen on exposure |
| Administration route | Parenteral | Oral | Parenteral | Parenteral |
| Dosing schedule | 0.25 ml/dose for <10 yr 0.5 ml/dose for ≥10 yr Two doses; two-four week apart | Four doses; one capsule each on alternate days | A single intramuscular injection of 0.5 ml | Two doses; four weeks apart |
| Target population for licensure | ≥6 months of age | Adults and children more than six years of age | Adults and children more than two years of age | Six months and above |
| Safety | Local side effects such as pain, swelling, redness and systemic side effects such as high-grade fever, chills, headache, vomiting and body ache are seen in 30-50% vaccines | Major safety concerns not reported | Major safety concerns not reported | Major safety concerns not reported |
| Contraindication | Acute severe febrile illness | Acute severe febrile illness. Congenital or acquired immunodeficient state which includes treatment with immunosuppressive drugs; acute gastrointestinal illness Individuals receiving sulphonamides and antibiotics | Acute severe febrile illness | Acute severe febrile illness |
| Efficacy | ~70% for three years | 80% at five years; 62% at seven years | 64-77% | 92-99% |
| Length of protection | At least three years | At least five-seven years | At least three years | Three-year follow up ongoing |
P. aeruginosa, Pseudomonas aeruginosa; rEPA, recombinant exoprotein A; IgA, immunoglobulin A; IgG, immunoglobulin G Source: Ref 43