Table 1.

The pros and cons of typhoid vaccine approaches

Vaccine type	Brands	Pros	Cons
Live attenuated Salmonella Typhi strain Ty21a	Vivotif oral	• Relatively low cost	• Requires 3 doses • Only indicated in children aged >6 years • Contraindicated in primary and acquired immunodeficiency • Cannot be given at the same time as antibiotics • Frequent gastrointestinal side effects • Contains bovine-derived material • May have weak or no efficacy • Cannot be adjuvanted because it is a live vaccine
Pure Vi polysaccharide vaccine	Typhim Vi®, Typherix®, and Typbar®	• High safety • Only a single dose is required	• Weak efficacy at ~50% • Only indicated in infants aged >2 years of age • Short duration of protection (<2 years) • Unable to boost response • Cannot be adjuvanted as it is T-cell independent
Vi polysaccharide conjugate vaccine	Typbar-TCV™	• High safety • More durable protection • Effective in children aged >3 months • 3- to 6-fold higher peak anti-Vi responses • Can potentially be adjuvanted	• More expensive • Protection would wane after 5 years
Protein capsular matrix vaccine	Typhax/Advax-CpG™	• High safety • Up to 1000-fold higher peak anti-Vi responses, suggesting the possibility of long-term protection • Inclusion of Advax-CpG adjuvant overcomes polysaccharide-associated immune suppression • Anti-Vi antibodies able to be strongly boosted with repeated doses • Induces serum bactericidal antibodies • Low cost	• None