Comparison of Diphtheria Cases in Children Before and During the Pandemic Era in Surabaya, Indonesia: A Study of Six-Year Data

Introduction Indonesia has a high incidence of diphtheria, especially in children. Surabaya has become a government regional reference center, as it is the capital of East Java province, which has the highest rate of diphtheria across the 38 regions. The aim of this study is to report our six-year pediatric diphtheria data, focusing on comparisons between before and during the pandemic era. Method This surveillance report was collected from community health centers and hospitals throughout Surabaya from January 1, 2017 to December 31, 2022. Collected data included demographic characteristics, clinical and laboratory aspects, the health centers, immunization history, and management. As per Indonesian guidelines, the diagnosis of diphtheria in this country requires a positive microbiological culture or approval from the National Experts on Diphtheria Committee. Results In total, there were 112 cases, of which 89 were found before the pandemic era. Although the number of cases declined during 2020-2022, the predominant age group, the immunization status, and the most common type of diphtheria remained consistent with pre-pandemic trends. Most cases had incomplete immunization or unimmunized children (67.8%), with the age group of 5-12 years old (44.6%), and with tonsillar diphtheria (83%). The case fatality ratio was 1.8%. Regarding the biovar of <i>Corynebacterium diphtheriae</i>, gravis is the most frequent finding. Conclusion The incidence of diphtheria cases in children in Surabaya was significantly lower during the pandemic. Although immunization coverage was not better, preventive measures during the pandemic may have played a role. Most patients did not have complete immunization histories during the study period, and the predominant type was tonsillar diphtheria. Since the trend in 2021-2022 increased, routine surveillance is essential.