Comparative immune response of Typbar TCV® (typhoid conjugate vaccine) in extremes of age: An Indian experience

Area of Science:

• Immunology
• Vaccinology
• Public Health

Background:

• Typhoid fever remains a critical global health issue, particularly in low- and middle-income countries.
• Typhoid Conjugate Vaccines (TCV) offer extended protection, especially for vulnerable young populations.
• Existing vaccines necessitate ongoing research for improved efficacy and broader age group application.

Purpose of the Study:

• To evaluate the immunogenicity and safety of Typbar TCV® in children compared to Typhim Vi®.
• To assess the safety and immunogenicity of Typbar TCV® in a broad age range, including elderly individuals.
• To investigate the impact of booster timing on the immune response to Typbar TCV®.

Main Methods:

• A comparator study enrolled 340 children, comparing Typbar TCV® to Typhim Vi®, with a subset receiving a booster dose.
• An age extension study involved 300 healthy volunteers across different age groups (18-85+ years) receiving a single Typbar TCV® dose.
• Antibody titers (anti-Vi-IgG) and adverse events were monitored in both studies.

Main Results:

• Typbar TCV® induced significantly higher anti-Vi-IgG titers than Typhim Vi® in children at days 28 and 90.
• No significant differences in adverse events were observed between vaccine groups in the comparator study.
• Typbar TCV® was well-tolerated and showed sustained antibody responses in children; a delayed booster (2 years) demonstrated enhanced immunogenicity compared to an early booster (6 months).
• In the age extension study, Typbar TCV® was safe and elicited comparable antibody titers in both younger and elderly adults.

Conclusions:

• Typbar TCV® is a safe and effective vaccine, demonstrating superior immunogenicity to Typhim Vi® in children.
• The vaccine is suitable for a wide age range, from 6 months to over 85 years.
• Optimal booster timing may enhance the long-term protective immune response.