Vaccination against typhoid fever: present status

Area of Science:

• Immunology
• Infectious Diseases
• Vaccinology

Background:

• Typhoid fever is a significant global health issue, particularly in developing nations, causing substantial mortality.
• Traditional whole-cell typhoid vaccines have limitations due to reactogenicity, driving research into oral alternatives.
• Current research focuses on live oral vaccines and purified antigens for improved typhoid fever prevention.

Purpose of the Study:

• To review the efficacy and safety of existing typhoid fever vaccines.
• To assess the potential of oral typhoid vaccines for public health control programs.
• To identify areas for future research, including novel vaccine development and co-administration studies.

Main Methods:

• Review of clinical studies on oral live Ty21a vaccine.
• Analysis of data for Vi polysaccharide vaccine efficacy and immunogenicity.
• Examination of research on genetically engineered live typhoid vaccines.

Main Results:

• The liquid formulation of the oral Ty21a vaccine demonstrated over 60% protection for 7 years.
• The Vi polysaccharide vaccine provided over 65% protection, maintaining high antibody levels for 3 years.
• Genetically engineered live oral vaccines show promising initial results but require further development.

Conclusions:

• Oral Ty21a and Vi polysaccharide vaccines are strong candidates for typhoid fever control programs.
• Further evaluation of safety and efficacy in Expanded Program on Immunization (EPI)-targeted age groups is crucial.
• Investigating vaccine interference with simultaneously administered vaccines, such as measles vaccine, is necessary.