What It Is
Typhoid Conjugate Vaccine (TCV) is an injectable vaccine against typhoid fever caused by Salmonella Typhi.
It links the Vi capsular polysaccharide antigen of S. Typhi to a carrier protein. This conjugation converts a relatively weak polysaccharide response into a stronger T-cell-dependent immune response, producing:
- better immune memory;
- longer protection;
- stronger response in infants and young children.
WHO currently prefers TCV over older typhoid vaccines for routine programme use because of these immunological advantages.
Why TCV Is Better Than Older Typhoid Vaccines
Older vaccines include the Vi polysaccharide vaccine and oral Ty21a vaccine.
Their limitations include:
- use mainly in older children or adults;
- shorter duration of protection;
- weaker immune memory;
- need for repeated doses or boosters.
TCV can be given from 6 months of age and is suitable for routine childhood immunisation. WHO also recommends its use in endemic settings and prioritisation where typhoid burden or antimicrobial resistance is high.
Public-Health Importance
TCV has importance beyond preventing individual infection.
By reducing typhoid incidence, it can also reduce:
- hospitalisation;
- community transmission;
- antibiotic consumption;
- selection pressure driving antimicrobial resistance.
This is particularly relevant because multidrug-resistant and extensively drug-resistant S. Typhi strains have complicated treatment in parts of South Asia.
WHO therefore treats TCV as part of both typhoid control and antimicrobial-resistance reduction.
India’s Role
India is important not only because typhoid remains a public-health concern, but also because it is a major producer of TCVs.
Two WHO-prequalified Indian vaccines include:
- Typbar-TCV, manufactured by Bharat Biotech and WHO-prequalified in 2017;
- TYPHIBEV, manufactured by Biological E and WHO-prequalified in 2020.
Typbar-TCV was the first typhoid conjugate vaccine to receive WHO prequalification, making it eligible for procurement by UN agencies and supporting introduction in lower-income countries.
Limitations and the Larger Control Strategy
TCV protects against Salmonella Typhi, not against S. Paratyphi A, an important cause of paratyphoid fever in South Asia.
Vaccination also cannot substitute for improvements in:
- safe drinking water;
- sanitation;
- food hygiene;
- disease surveillance;
- accurate diagnosis;
- antimicrobial stewardship.
WHO explicitly recommends that typhoid vaccination programmes be implemented alongside water, sanitation, hygiene and improved clinical management.
The most effective approach is therefore a combination of vaccination, WASH, surveillance and responsible antibiotic use, rather than reliance on vaccination alone.
