Evaluation of invalid vaccine doses.

Area of Science:

• Pediatric Health
• Immunization Practices
• Public Health Policy

Background:

• The 2002 Recommended Childhood Immunization Schedule defined invalid vaccine doses as those administered 5 or more days before the minimum age or interval.
• Invalid vaccine doses require repetition to ensure adequate immunization coverage.

Purpose of the Study:

• To determine the proportion of U.S. children receiving invalid vaccine doses.
• To assess the impact of excluding invalid doses on vaccination coverage rates.
• To estimate the cost of revaccinating children who received invalid doses.

Main Methods:

• Analysis of provider-reported vaccination histories from the 2000 National Immunization Survey for children aged 19–35 months.
• Classification of vaccine doses administered ≥5 days before the recommended minimum age or interval as invalid.
• Comparison of vaccination coverage with and without counting invalid doses.

Main Results:

• 10.5% of children received at least one invalid vaccine dose.
• Hepatitis B (51%) and diphtheria-tetanus-pertussis (19%) were the most common invalid doses.
• Excluding invalid doses resulted in minor coverage changes, but revaccination costs ranged from $10–$18 million.

Conclusions:

• An estimated 595,000 children received invalid vaccine doses, incurring substantial revaccination costs.
• The financial burden of repeating invalid doses impacts parents, physicians, and purchasers.
• Provider education on immunization timing is essential to minimize invalid vaccine administration.