Diphtheria immunogenicity following the administration of pentavalent DTwP-HB-Hib vaccine at 4- and 8-week intervals: A randomized controlled trial

Objective: To evaluate the effectiveness of DTwP-HB-Hib vaccination dosing intervals at eight weeks versus four weeks on the immunogenicity of the diphtheria component. Methods: This is a randomized, open-label, parallel, controlled trial on healthy two-month-old infants who had not received DTwP-HB- Hib vaccinations. The infants received three doses of the vaccine either at an eight-week or four-week interval. The anti-diphtheria toxoid IgG antibody levels before and after three doses of the vaccination were measured using ELISA. Results: Eighty infants were enrolled in this study, with 64 fulfilling the study requirements and randomized into two groups. All study participants exhibited uncertain protection against diphtheria antibodies (0.01-0.99 IU/mL) at the beginning of the study with an average of (0.023±0.009) IU/mL and (0.026±0.009) IU/mL in eight weeks and four weeks groups. Following three doses of the vaccination, the antibody level rose to an average of (1.320±0.234) IU/mL in the eight-week group and (1.307±0.186) IU/mL in the four-week group, with no statistically significant difference in the antibody levels observed (P=0.814). Conclusions: DTwP-HB-Hib vaccinations can be administered at an eight-week or four-week interval, as they do not significantly affect the level of anti-diphtheria IgG antibodies.