Safe and effective booster immunization using DTaP in teenagers.

The incidence of reported cases with pertussis has increased in young adults in Japan and the lack of additional booster immunizations containing pertussis components is suspected to be one of the causal reasons. Instead of DT immunization at 11–12 years of age, safety and immunogenicity were investigated using 0.2ml and 0.5ml of DTaP. 176 subjects in DTaP 0.5ml, 178 in DTaP 0.2ml, and 197 in DT 0.1ml groups were enrolled in clinical trial. The relative risk of local reactions in the DTaP 0.2ml group compared to the DT 0.1ml group was 1.13 (95% CI: 0.97–1.30), and that of the DTaP 0.5ml to the DT 0.1ml group was 1.34 (95% CI: 1.18–1.53). The relative risks of local pain and heat were 1.62 (95% CI: 1.33–1.98) and 1.59 (95% CI: 1.19–2.13), respectively, in the DTaP 0.5ml group compared to the DT 0.1ml group. Sero-positive rates against PT and FHA were 54% and 82% before immunization and increased to >95% for both after vaccination with no significant difference in GMT. Instead of the scheduled DT program, 0.2ml of DTaP was acceptable and demonstrated efficient immunogenicity.