Predictors of age-appropriate receipt of DTaP Dose 4 Original Research Article

Background In the United States, the national childhood immunization schedule calls for children to receive four doses of DTaP (diphtheria and tetanus toxoids and acellular pertussis) vaccine administered at 2, 4, 6, and 15 to 18 months. Dose 4 of DTaP is among the most frequently missed vaccines for children who are not adequately immunized. Methods Using the 2001 National Immunization Survey, the effect of the timeliness of the first three DTaP doses was assessed on completion of the four-dose series by age 24 months and on time by age 12 to 18 months. Results Missing Dose 4 was more prevalent among children who received Dose 3 late (but <16 months) than among children who received Dose 3 on time (24% vs 10%). Similarly, receiving Dose 4 late (or not at all) was more prevalent among children who received Dose 3 late (but <9 months) (39% vs 22%). An invalid Dose 4 was administered to 4.6% of those with Dose 3 late but before 9 months and to 10.6% of those with no Dose 3 before 9 months, compared to 1.2% of those with Dose 3 on time. Conclusion Physicians and staff can identify children at risk for missing the fourth DTaP dose or receiving it late by assessing timeliness of receipt of DTaP Dose 3 and implementing steps to ensure that at-risk children receive Dose 4 as recommended.