Changes in vaccination practices among infants after the introduction of DTaP-IPV/Hib combination vaccines

Abstract

Background: Diphtheria-tetanus-acellular pertussis, polio, and Haemophilus influenza type B (DTaP-IPV/Hib) combination vaccine was introduced as a part of the Korea National Immunization Program (NIP) on June 19, 2017. Combination vaccines can improve vaccination rates by simplifying the vaccination schedule. Objective: To explain how the introduction of DTaP-IPV/Hib in the NIP has changed vaccination practices for infants. Methods: Using a nationwide vaccine registry, the proportion of infants who completed the full recommended doses of the primary series of DTaP, IPV, and Hib (D-I-H) within 12 months of age was estimated among those born between 2013 and 2019. Among those, the proportions of those who received the same DTaP components for all 3 doses during the primary series were calculated for the 2013–2016 and the 2017–2019 birth cohorts. Those who received the same component of DTaP throughout the entire primary vaccination schedule were categorized into 3 groups by DTaP components to compare the average frequency of medical visits for vaccination. Results: A total of 2,703,822 infants were born between 2013 and 2019, of which 96.7% completed full doses of the primary D-I-H series within 12 months of age. For the 2013–2016 birth cohorts, most received DTaP-IPV-only (75.4%), while most of the 2017–2019 birth cohorts received DTaP-IPV/Hib-only (81.0%) to complete the 3 doses for primary D-I-H series. The average frequency of medical visits for vaccination showed a significant difference across the 3 groups classified by DTaP components in every birth cohort (p < 0.001). Conclusions: After the introduction of DTaP-IPV/Hib, most infants completed the primary D-I-H series with the combination vaccine and there was a significant reduction in the average number of medical visits for vaccination. Our findings provide important insights for countries considering the introduction of combination vaccines into their NIP. © 2024 The Authors