Diphtheria-tetanus-acellular pertussis vaccine safety in children under 7 years: a post-marketing analysis of the U.S. vaccine adverse event reporting system.

Objectives: Although Diphtheria-Tetanus-acellular Pertussis (DTaP) vaccines have been used in the U.S. for decades and have extensive safety records, a comprehensive post-marketing assessment for all available types is still needed. This study leveraged the Vaccine Adverse Event Reporting System (VAERS) database to evaluate adverse events following immunization (AEFI) and analyze potential associations with vaccine administration. Methods: We extracted all reports of adverse events (AEs) following DTaP vaccination from the VAERS database for the period 1990 to May 2025. Our analysis included descriptive statistics to summarize patient demographics and clinical features, and disproportionality methods to identify potential safety signals. Results: During the study period, the VAERS database documented 57,341 children under 7 years who received DTaP vaccines, corresponding to 57,368 administered doses and 193,955 adverse event (AE) reports. AE reporting was more frequent in males (52.46%) than females (45.07%), with more than half of the cases (50.44%) involving children under 2 years old. The most common clinical outcomes were recovery (62.53%) and hospitalization (10.29%). Most AEs (89.61%) occurred within 0-30 days after vaccination, with a median onset time of 1.0 days. Infanrix (37.95%) and Daptacel (25.04%) were the most frequently reported vaccine types. Disproportionality analysis detected 158 positive AE signals across 24 system organ classes (SOCs). Among all SAEs, pyrexia (ROR = 1.01) was the most frequently reported, followed by convulsion (ROR = 1.82) and vomiting (ROR = 1.05). The most common signals for non-SAEs included injection site erythema (ROR = 3.79), injection site swelling (ROR = 3.00), and erythema (ROR = 3.03). Conclusions: This post-marketing surveillance indicates that most reported AEs were non-serious and occurred within 30 days following vaccination. These findings support the known safety profile of DTaP vaccines and highlight identifiable timing patterns of AEs, which may help inform monitoring strategies and benefit-risk assessments after immunization.