Unintended vaccination of pregnant adolescents: Estimating the scope of the problem and the impact of different pregnancy testing strategies

Among a hypothetical cohort of 11-18-year-old females, we used a probabilistic decision tree model to estimate the number of pregnant adolescent females potentially receiving contraindicated vaccines during well child exams, and to determine the impact of two different pregnancy screening strategies on pregnancy detection rates, vaccine administration and pregnancy detection-associated costs. We found that under current practice conditions, the majority (95-99%) of adolescent pregnancies are likely missed during well child exams, allowing the opportunity to administer contraindicated vaccines. A strategy to test everyone detected the highest proportion of pregnancies, but at a substantial financial cost ($12,270,037-$19,430,607). Testing was more efficient for older adolescents, but both testing strategies were associated with a significant number of false positive test results (41-98%), regardless of age. These results suggest that systematic pregnancy screening strategies would be effective for preventing pregnant adolescents from receiving contraindicated vaccines, but may not be worth the potentially high financial and psychological costs.