Typhoid fever vaccines
Challenges and related links
Challenges to the use of current typhoid vaccines
Challenges to the widespread use of currently available typhoid vaccines include:
- The relatively short duration of protection and the need for repeat doses (every 3 years for Vi-PS, and every 5 to 7 years for Ty21a vaccines);
- The vaccines cannot be given to children under 2 years of age;
- The difficulty of defining “risk groups” for targeted vaccination: as typhoid is a focal disease, immunization may not be justified nationwide;
- The relative high cost of the vaccines.
Future typhoid vaccines
It is hoped that a conjugate typhoid vaccine may be licensed by 2015, primarily because this formulation could be integrated into infant immunization schedules and provide long-term protection. Several vaccine manufacturers are developing Vi-conjugate vaccines using either TT, DT or the CRM197 protein carriers. Guidelines for quality, safety and efficacy assessment of conjugated typhoid vaccines are currently being developed by IVB’s QSS team.
IVR activities
IVR is a member of a global forum of interested partners called the Coalition against Typhoid (see link below), coordinated by the Sabin Vaccine Institute with members from global public health, industry, academia and donors among others.
WHO provides technical and seed funding to countries to strengthen typhoid surveillance for improved epidemiology and disease burden data, and guidance on vaccine introduction and impact assessment. In addition to the SAGE policy on vaccine use, WHO is updating the Background document: the diagnosis, treatment and prevention of typhoid fever, and developing new guidelines on the quality, safety and efficacy of typhoid conjugate vaccines.
Finally, to ensure wide access to available typhoid vaccines, WHO prequalifies typhoid vaccines that meet global standards of safety and quality.