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December 10th, 2001

Important information on VAQTA
(Hepatitis A vaccine, Inactivated) in prefilled syringes

Dear Doctor/Health Care Provider,

Re-tests of VAQTA (Hepatitis A vaccine, Inactivated) in prefilled syringes have revealed a decreased antigen content in some syringes below the established minimum specification. As a result, a possibility exists that persons vaccinated with VAQTA in prefilled syringes from the indicated lots may be insufficiently protected against Hepatitis A.

Merck & Co., Inc. is voluntarily recalling the indicated lots (see Attachment I for all indicated lots) of VAQTA in prefilled syringes. Patients who may have received doses from the indicated lots would have been vaccinated after May 29, 2001 with the adult formulation (50U/1 mL), and after August 9, 1999 with the pediatric/adolescent formulation, (25U/0.5 mL).

The indicated lots should no longer be used. You are kindly requested to return any stock of the recalled VAQTA in prefilled syringes to Merck according to the enclosed instructions or if not purchased directly from Merck, to your distributor. Cold chain transport is not necessary.

The following are not affected by this recall:

• All VAQTA packaged in vials, and
• Lots of VAQTA packaged in syringes not on the attached list.

If you have questions with respect to returns please contact the Merck order management center at 1-800-637-2579.

For individuals vaccinated with prefilled syringes from indicated lots:

It is suggested that you review the records of patients who may have been vaccinated after the following dates with VAQTA in prefilled syringes, to see if the indicated lots were used in such vaccination:

• Adult formulation (50U/1 mL): May 29, 2001
• Pediatric/adolescent formulation (25U/0.5 mL): August 9, 1999

If in your clinical assessment, revaccination against Hepatitis A and/or antibody testing is indicated for these patients, you may consider the following guidelines:

In order to determine the immunogenicity of the indicated lots of vaccine administered to your patient, Merck & Co., Inc. is negotiating a contract with a testing laboratory to determine the Hepatitis A antibody concentration in these patients. If you choose to do antibody testing, the service by this laboratory will be free. Please contact Merck & Co., Inc. via telephone for a complete set of instructions.

Telephone number: 1-800-439-4958

If revaccination doses are necessary, contact Merck & Co., Inc. via fax regarding re-supply of vaccine free of charge. Please send your written request to the following fax number, indicating the number of revaccination doses used and identifying your source of supply.

Fax number: 215-652-6700

For medical questions please call the Merck National Service Center at 1-800-672-6372.

Before prescribing, please read the enclosed prescribing information for VAQTA (Hepatitis A Vaccine, Inactivated).

We do hope that you will understand these necessary measures.

Kind regards,

Thomas M. Vernon, M.D.

VP Policy, Public Health & Medical Affairs

Attachment 1 - Table of Recalled Lots

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