Merck & Co. Inc. said yesterday that equipment upgrades at its West Point plant would cause shortages of its hepatitis B vaccine for adults.

Merck said the shortages would not affect pediatric versions of the vaccine.

The Centers for Disease Control and Prevention said Merck competitor GlaxoSmithKline P.L.C. was producing enough hepatitis B vaccine to compensate for shortfalls.

Merck spokeswoman Amy Rose said the firm was not answering questions about what the upgrade included or whether it was planned.

"For competitive reasons, we'd prefer not to provide any details," she said. "This situation does not, in any way, impact the quality or safety of Recombivax HB now available on the market."

She could not say when Merck expected to meet demand again for the adult vaccine, sold as Recombivax HB, but she said it would be "in a timely manner."

Rose said the shortage was not related to an FDA warning in April that manufacturing practices at the Merck plant did not meet the agency's standards. The firm has said those issues have been resolved.

Merck, which is based in Whitehouse Station, N.J., also has had shortages of its Zostavax shingles vaccine because of problems with the materials used to make it. That sent Zostavax's third-quarter sales down 82 percent to $11 million. Merck's combined sales for its hepatitis vaccines Recombivax and Vaqta were $36 million for the third quarter.

Rose said the two shortages were unrelated. The company has said it hopes to eliminate back orders for Zostavax by the end of this year.

Doctors typically vaccinate children in the United States for hepatitis B, which can be transmitted through bodily fluids and attacks the liver. Adults get the vaccine only if they are at risk for exposure because of their jobs, lifestyle or travel.