IMS Health continues to assess a data-supply glitch that led to an underreporting of ­prescriptions for Vertex Pharmaceuticals’ hepatitis C drug Incivek.

During the period in question—the last two weeks of September—IMS data showed relatively flat TRx of the drug. Various financial analysts interpreted the dip as a sign that usage of the new drug had peaked.

Instead, IMS said, a key supplier had missed some mail order prescriptions. IMS adjusted for the issue but due to the short duration is not restating the history, a spokseman for the company said.

But when the company initially disclosed the hitch, Vertex shares jumped 7% as investors expected that a new sales report would reflect more comprehensive estimates. Then, when new IMS data still did not show sales had risen, shares declined by more than 6%.

As of early October, Incivek scripts continued to climb. Vertex is battling Merck’s Victrelis for hep-C market share.

Because of IMS’s script-reporting issues, rival Rx tracker Wolters Kluwer said it verified the quality of data it received from vendors for Incivek and Victrelis, saying it had not experienced a significant loss of data and continued to receive “a consistent data flow.”

A Vertex spokesperson said the firm doesn’t comment on IMS data.