Vaccine INDs: review of clinical holds.

A sponsor developing a vaccine or related product for clinical study in the U.S. must submit an Investigational New Drug Application (IND) to the Food and Drug Administration (FDA). Evaluation of information submitted to the IND may prompt a clinical hold, for reasons described in 21 CFR 312.42. Our review of clinical hold letters issued to sponsors during a 2-year period identified the most often cited reason for a clinical hold, insufficient information (21 CFR 312.42 (b) (1) (iv)), and indicated that the majority of INDs were specifically deficient in clinical information. In addition, sponsors who sought formal pre-IND advice decreased the likelihood of their resulting IND being placed on clinical hold.