The Food and Drug Administration has ordered Merck & Co. to correct numerous manufacturing deficiencies at its main vaccine plant, the latest in a string of setbacks for the drugmaker.
The agency on Wednesday released a warning letter sent to Merck's chief executive, Richard T. Clark, that states FDA inspectors determined manufacturing rules are not being followed at the plant in West Point, Pa., just outside Philadelphia.
The plant, which recalled two vaccines in December over sterility problems, makes a number of children's vaccines and four for adults.
The nine-page letter states FDA found "significant objectionable conditions" in the manufacture of vaccines and drug ingredients during repeated inspections from Nov. 26 to Jan. 17.
In a separate posting on its Web site, the agency said it issued the warning letter because Merck's response to the FDA report sent after the inspections was "inadequate to address the serious deviations noted."
According to the heavily redacted warning letter, Merck officials didn't thoroughly investigate when vaccine batches inexplicably failed to meet specifications, even if batches had been distributed, and some combination measles-mumps-rubella shots that failed "visual inspection for critical defects" were distributed anyway.
The letter also said the plant didn't have written procedures, tests or other laboratory controls to ensure "identity, strength, quality, and purity" of products.
However, in the Web site posting, the FDA said it "does not believe that the issues identified will affect the safety of the vaccines" made at West Point, or their availability.
"We're committed to working with the FDA to ensure that all these issues are addressed to their full satisfaction," said Merck spokeswoman Amy Rose, who added that the company does not distribute contaminated products.
"We are confident in the quality, effectiveness and safety of our medicines and vaccines," she said.
Rose said Merck would be submitting additional information to the FDA and discussing it in a meeting, which is requested in the warning letter. The letter was signed by David K. Elder, head of enforcement in the agency's Office of Regulatory Affairs.
Merck shares, hammered by FDA rejecting two of its experimental drugs since Friday, initially dropped about $1 on the news, then recovered. They ended Wednesday up 90 cents, or 2.4 percent, to $38.04.
The warning letter gives Merck 15 days to tell the FDA how it will correct the violations. If Merck does not comply, the letter states the FDA can take actions including suspending or revoking the plant's manufacturing license, seizing products or seeking injunctions, such as against product shipments.
"Warning letters help achieve voluntary compliance," FDA spokeswoman Mary Long said in an e-mail response to questions from The Associated Press. "Further action can be taken in the event violations remain uncorrected and would depend on the details of a given situation."
Production of two vaccines made at West Point _ PedvaxHIB, to prevent Haemophilus influenza type B, and Comvax, a combination vaccine for Haemophilus B and hepatitis B _ stopped last year and 1.2 million doses of them were recalled after a sterility problem was discovered in October.
The plant also makes ProQuad, which protects children against measles, mumps, rubella and chickenpox; hepatitis A, hepatitis B and meningitis vaccines for children and adults; and Gardasil, to protect young women against cervical cancer.