Merck & Co. is recalling about a million doses of a childhood vaccine, after testing showed a sterilization problem in a Pennsylvania factory. 
The company is not aware of any harm to children who received the vaccine, known as Hib, which prevents meningitis and pneumonia. It is a three-dose shot recommended for all children under 5 and is usually given to infants starting at two months old.
The recall involves 10 lots of Hib vaccine and two lots of a combination vaccine for both Hib and hepatitis B, a Merck spokeswoman said.