Table 2. Advantages and disadvantages of past, present and future vaccines against Salmonella enterica.

Vaccine	Advantages	Disadvantages
A Vaccines of the Past
Whole Cell Inactivated	73% 3-y efficacy	Reactogenicity
B Established Vaccines
1. Vi CPS	Single dose	Not licensed for infants
	Low reactogenicity	Lack of memory response
	WHO prequalification	Lack of affinity maturation
		Only protects against S. Typhi
2. Ty21a	Oral administration	Not licensed for infants
	Some cross-protection against	Requires multiple doses
	S. Paratyphi B
C New and Future Vaccines
1. Vi glycoconjugate	Higher efficacy than current vaccines	Only protects against S. Typhi
	T-dependent antibody response
	Memory induction
	Affinity maturation
	Low reactogenicity
2. O-antigen glycoconjugate	As for Vi glycoconjugates	Only protects against serovars with same O-antigen specificity
3. New Live Attenuated	Salmonella-specific B and T cell immunity	Attenuating for optimal balance of immunity and reactogenicity
	Clearance of residual infection	Breadth of coverage may be limited by insufficient expression of key antigens
		Possibility of disease in immunocompromised subjects
4. Recombinant Proteins	Salmonella-specific B and T cell immunity	Issues with antigen conformation may limit ability to induce effective B cell response
	Potential for pan-specific immunity
	Low reactogenicity
5. Proteins purified from whole Salmonellae	Salmonella-specific B and T cell immunity	Difficulties with purification of integral membrane proteins
	Potential for pan-specific immunity
	Low reactogenicity
6. GMMA	Salmonella-specific B and T cell immunity	Balance of reactogenicity and immunogenicity in man not currently known
	Potential for pan-specific immunity
	Enrichment of membrane antigens
	Ease of manufacture Low cost-of-goods

Adapted with permission from reference ⁴⁷.