Persistent high diphtheria positivity in North India: Evidence from a tertiary hospital-based study, 2007-2021

Area of Science:

• Infectious Diseases
• Epidemiology
• Public Health

Background:

• Diphtheria continues to cause significant morbidity and mortality in India despite available vaccines.
• Hospital-based data from a tertiary care infectious disease hospital in northern India were analyzed over 15 years.
• The study aimed to describe the epidemiology of diphtheria in the region.

Purpose of the Study:

• To analyze 15 years of hospital data on suspected diphtheria cases in northern India.
• To describe the epidemiology of diphtheria, including demographic characteristics, vaccination status, and clinical outcomes.
• To examine the association between vaccination status and culture-confirmed diphtheria.

Main Methods:

• Analysis of hospital records for suspected diphtheria cases (January 2007-December 2021).
• Inclusion criteria: upper respiratory tract illness with an adherent membrane.
• Multivariable logistic regression used to assess the impact of vaccination status on confirmed diphtheria.

Main Results:

• Over 5,493 suspected cases, 2,131 (38.8%) were culture-confirmed for C. diphtheriae.
• A high case-fatality ratio of 19.1% (408 deaths) was observed.
• Only 1.1% of cases were fully vaccinated; unvaccinated/partially vaccinated individuals had significantly higher odds of diphtheria.

Conclusions:

• Sustained high diphtheria positivity indicates ongoing transmission in northern India.
• Immunity gaps, likely due to suboptimal booster vaccine coverage, are driving transmission.
• Strengthening immunization programs with a focus on timely booster doses is crucial to reduce diphtheria transmission.