Merck issues a recall on the common children's vaccine Hib, which guards against meningitis, pneumonia, and other serious infections. It's routinely administered to babies beginning around two months of age. The recall covers about 1.2 million doses of the vaccine distributed since April. The recall comes after concerns over risks of contamination at a Pennsylvania factory. So far there haven't been any reports of contaminated vaccines. Officials say they do not know of a health threat. But there are concerns about a shortage of Hib vaccine. A Merck official said that the company will not be able to supply any vaccine for at least nine months.