Merck & Co. is recalling about 1.2 million doses of a childhood vaccine designed to protect children against meningitis, pneumonia and other severe diseases after the company discovered a bacteria in the equipment used to make the vaccine.

Merck is one of the two providers of the vaccine also known as Hib vaccine, which is administrated to children in three doses, at the age of 2 months, 4 months and 12 months. The company said it recalled 11 lots of PedvaxHIB vaccine and 2 lots of its Comvax vaccine because there was no assurance regarding the sterility of the product.

Both vaccines were manufactured in West Point, Pennsylvania and distributed starting with April 2007. Except one lot, all vaccines were distributed in the United States, the company said.

"The potential for contamination of any individual vaccine is low, and, if present, the level of contamination would be low," Merck said.

The vaccine is designed to protect against illnesses caused by the bacterium Haemophilus influezae type B and is unrelated to seasonal influenza, health officials said.

"The CDC and FDA learned this week that Merck, one of two companies that provide Hib vaccine, is recalling certain lots of the vaccine. Right now, this is not a health-threatening situation for children. The recall has nothing to do with the potency of the vaccine, so children who have received the vaccine are protected," Dr. Julie Gerberding, director of the U.S. Centers for Disease Control and Prevention, said during a late afternoon teleconference.

Parents were advised to look for signs of infection at the place of the inoculation in the days following the injection though.

At the same teleconference, Dr. Norman Baylor, director of the U.S. Food and Drug Administration’s Office of Vaccine Research and Review said Merck had identified the problem during a routine testing of the manufacturing process in Pennsylvania.

"Merck identified an issue that creates the potential for microorganisms to survive a sterilization step performed during manufacturing. No documented contamination of the vaccine has been found." Baylor said.

Health officials urged the other provider of the vaccine, Sanofi Pasteur to boost supplies in a bid to fill the gap caused by the recall.

"We do expect there to be a shortage. The extent of that we're trying to find out," said Dr. Anne Schuchat, director of the CDC’s National Center for Immunization and Respiratory Diseases. She also added that the recall would not pose an immediate health risk because more than 90 percent of children in the U.S. have already received the vaccine.

About 14 million Hib doses are needed annually to vaccinate children according to the CDC.