Based on an unpublished FDA report the newspaper obtained through a Freedom of Information Act request, the article said inspectors found 49 areas of concern, ranging from failure to follow good management practices to contamination of bulk lots of vaccine.
FDA inspectors visited the plant, in West Point in Montgomery County, on 30 separate days from November through January.
In December, Merck recalled 1.2 million doses of its vaccine against Haemophilus influenza type B, made at the same plant, because of a sterility problem discovered in October. It also quarantined nearly a year's worth of other, possibly suspect doses.
Merck executive John McCubbins, head of Merck's Global Vaccine Manufacturing and West Point operations, told the newspaper no contamination was found in finished vaccines and that the company is addressing the problems.
"We are absolutely confident in the quality of the products," McCubbins told the newspaper, adding that Merck technicians detected and reported most of the problems, which were found in the manufacturing process.
The FDA has not ordered the Whitehouse Station, N.J.-based company to stop production and is reviewing Merck's responses to the report, Amy Rose, Merck's director of media relations, said Thursday. She termed the inspections routine.
"Nothing is more important to Merck than the quality and safety of our medicines and vaccines," she wrote in a follow-up e-mail.
Also Thursday, Deutsche Bank pharmaceuticals analyst Barbara Ryan wrote in a note to investors that the "deficiencies have been addressed and remediated with no consequences in terms of delays or shortages for any vaccine products."
"It is typical for FDA inspections to result in deficiencies" such as those in the report, Ryan added.
Merck is one of the few drugmakers that make vaccines and in recent years has launched four successful new ones, including Gardasil, to prevent cervical cancer. Last year, sales of all its vaccines totaled $4.3 billion.
"Merck has invested heavily in increasing our vaccine manufacturing capacity, training our employees and continuously improving our quality systems" as the new vaccines were launched, Rose wrote.
Meanwhile, a CDC spokesman said Thursday that the agency is not aware of problems with vaccines at the plant and so is not taking action.
In trading Thursday, Merck shares rose $1.35, or 3.5 percent, to $39.97, near the bottom of their 52-week range of $36.82 to $61.62.
