[Active surveillance of adverse event within 7 days of single versus simultaneous administration of diphtheria, tetanus, and acellular pertussis combined vaccine in children aged 2-month and 6-year-old].

Objective

To evaluate the safety of simultaneous administration of the diphtheria, tetanus, and acellular pertussis vaccine (DTaP), inactivated poliovirus vaccine (IPV), and group A and group C meningococcal polysaccharide vaccine (MPV-AC) in children aged 2-month and 6-year-old.

Methods

From June to July 2025, children at vaccination clinics in Wuxi City were enrolled, including 2-month-old children (receiving DTaP1 alone or combined with IPV1) and 6-year-old children (receiving DTaP5 alone or combined with MPV-AC2). The occurrence of adverse event (AE) within 7 days post-vaccination was observed, and the incidence, severity grading, symptoms, and intervals were compared. The comparison of the incidence of AE between groups was performed using the Chi-square test or Fisher's exact test.

Results

The incidence of AE in the 2-month-old group (1 688) was 7.35%, significantly lower than that in the 6-year-old group (2 348; 18.78%; χ²=106.675, P<0.001). Comparison of DTaP1 versus DTaP1+IPV1 showed no significant differences in the overall (6.85% vs. 7.53%, χ²=0.231, P=0.631), local (1.07% vs. 0.49%, P=0.189), or systemic (6.21% vs. 7.04%, χ²=0.370, P=0.543) AE rates. Similarly, no significant differences were observed in the overall (20.14% vs. 17.74%, χ²=2.182, P=0.140), local (18.38% vs. 16.08%, χ²=2.160, P=0.142), or systemic (3.91% vs. 3.40%, χ²=0.437, P=0.509) AE rates between the DTaP5 and DTaP5+MPV-AC2 groups. In the DTaP1 and DTaP1+IPV1 groups, systemic AE were predominantly grade 1, manifesting primarily as fever (1.07% vs. 2.78%, χ²=4.397, P=0.036), crying (1.71% vs. 1.97%, χ²=0.116, P=0.734), and decreased appetite/anorexia (1.07% vs. 1.15%, χ²=0.018, P=0.895). Notably, a statistically significant difference was observed only for fever. In the DTaP5 and DTaP5+MPV-AC2 groups, local AE were primarily grade 2, with the most common symptoms being redness and swelling (15.54% vs. 13.58%, χ²=1.791, P=0.181), pruritus (7.33% vs. 7.47%, χ²=0.017, P=0.898), pain (4.89% vs. 3.77%, χ²=1.757, P=0.185), and induration (4.20% vs. 3.47%, χ²=0.847, P=0.357). No significant differences were found in the incidence rates of any symptoms between the DTaP5 and DTaP5+MPV-AC2 groups. Redness and swelling, and induration predominantly presented as grade 2 reactions (≥5 cm in diameter). The majority of post-vaccination AE in all four groups occurred within ≤1 day after immunization.

Conclusion

Simultaneous administration of DTaP with IPV and MPV-AC shows a favorable safety profile, without an increase in the risk or severity of AE. Notably, 6-year-old children have a higher incidence of AE compared with 2-month-old children, primarily manifesting as increased local AE.