Of the five Minnesota cases, one child hadn't completed the primary series of shots, one had a weakened immune system, and in the three other cases -- including the child who died from meningitis in November -- parents had refused the vaccine, the officials said.
The news follows an announcement last November by U.S. health officials that a shortage of vaccine was leading them to monitor Hib infections, one of the most important causes of bacterial illness in young children.
Though federal officials said at the time that they had not yet seen an increase in cases, the stepped-up surveillance was prompted by a disruption in the supply of vaccine that has virtually eliminated Hib (Haemophilus influenzae type b) infections since it was introduced.
Hib infection can cause a variety of illnesses, including meningitis (inflammation of the membranes covering the spinal column and brain), blood stream infections, and pneumonia, according to the CDC. Hib is not a cause of the seasonal flu.
The shortfall was caused by a recall of certain lots of Hib conjugate vaccine, and then the suspension of production by drug maker Merck & Co. in December 2007. Merck originally expected to resume production late last year, but delays pushed that timetable back to the middle of this year, the CDC said in its Nov. 21, 2008, Morbidity and Mortality Weekly Report.
One reason the vaccine shortage hasn't been more serious is that drug maker Sanofi-Aventis also makes Hib vaccine.
Before the introduction of the vaccine, some 20,000 U.S. children would get serious and sometime fatal Hib infections each year, the CDC noted.
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