Introduction: Surveillance of vaccine-preventable diseases (VPDs) such as diphtheria and pertussis are vital for monitoring immunization program effectiveness. This study evaluates the performance of Tamil Nadu's surveillance system using data from the Vaccine Preventable Diseases Surveillance Information Management System (VSIMS) for 2023.
Methods : A cross-sectional analysis of suspected diphtheria (n=101) and pertussis (n=57) cases reported in Tamil Nadu during January-December 2023 was conducted. Indicators assessed included timely notification, investigation, sample collection, active case search (ACS), and follow-up. Performance was benchmarked against targets in the Diphtheria, Pertussis, and Neonatal Tetanus Surveillance Field Guide.
RESULTS : Timely notification exceeded the 80% target for both diseases, with 89.1% for diphtheria and 89.5% for pertussis cases. Timely investigations were conducted in 93.1% and 91.2% of diphtheria and pertussis cases, respectively. Adequate sample collection surpassed targets but was predominantly limited to single specimens. However, ACS performance was suboptimal, with only 33.7% for diphtheria and 17.5% for pertussis cases. Follow-up documentation was notably poor (27.7% for diphtheria, 8.8% for pertussis).
CONCLUSION : While the performance of the Diphtheria and Pertussis surveillance system in Tamil Nadu aligns with national targets for notification and investigation, ACS and follow-up documentation require significant improvement. Strengthening these areas is essential for identifying clustering, ensuring timely public health responses, and achieving Immunization Agenda 2030 goals.