Merck is recalling over a million doses of its Haemophilus influenzae Type B vaccine because of improper sterilization during manufacturing, according to the New York Times. Centers for Disease Control and Food and Drug Administration officials said there was no public health threat, although the recall may lead to a shortage of the vaccine this year.

The recall affects Pedvaxhib and the combination Haemophilus/hepatitis B vaccine Comvax  that were distributed as early as April 2007.

Merck says that physicians should not administer vaccines from the recalled lots. Patients who have already received the recalled vaccines should finish their series with an Hib conjugate-containing vaccine not part of this recall. Revaccination is not necessary, Merck says, because the vaccine's efficacy was not affected.

For further information, read the CDC's frequently asked questions on the recall.