Minnesota health officials are urging parents to make sure their babies are adequately vaccinated against Haemophilus influenzae B, a bacterial infection that can lead to severe illness and is sometimes fatal.
The warning was prompted by an unexpected surge of Hib in Minnesota last year.
"This is a preventable infection. We have to get this message out to everyone we can," said Dr. Ruth Lynfield, state epidemiologist.
In a teleconference briefing Friday, the Minnesota Department of Health said five cases were reported in 2008, one of them resulting in death.
"This is the highest number of cases that we have had since 1992, when conjugated vaccines for infants became widely available," Lynfield said.
Three of the five cases, including the child who died, had not been immunized against Hib. A fourth child had not completed the primary three-dose series of shots. The fifth case was in a child who had received the full series of shots but was later found to have an underlying immune-system condition.
Lynfield said the cases occurred in five different Minnesota counties and were not linked.
State Health Department officials and officials with the U.S. Centers for Disease Control and Prevention believe a national shortage of the Hib vaccine may be one of the contributing factors to the resurgence of the disease.
"In fact we have heard from our pediatricians, our family practice physicians, the nurses at the clinic, that they don't have enough vaccine in certain areas of the state," Lynfield said.
Because of the shortage, national advisory groups have been recommending deferral of a fourth and final booster shot for Hib among toddlers ages 12 to 15 months, so that as many infants as possible could receive the initial series of three shots.
"At that time we hoped we had a cushion of protection in the country to keep rates (of Hib) down," said Dr. Anne Schuchat, director of the National Center for Immunization and Respiratory Diseases.
This strategy appears to be working in most states. In Minnesota, however, there has been a drop in the overall number of children who've received the primary series of three Hib vaccinations -- even though the majority of them are still getting other recommended vaccinations.
Kristen Ehresmann, immunizations manager with the Minnesota Department of Health, said a review of the state immunization registry found that at 7 months, 63 percent of infants had received a third dose of the vaccine that protects against diphtheria, tetanus and whooping cough, but only 46 percent had received a third dose of the Hib vaccine.
In recent years, the number of parents opting out of vaccination has been increasing, Ehresmann said.
Health officials also noted that compared to other states, more Minnesota health care providers have been using a Hib vaccine manufactured by Merck, which is the one in shortest supply. So far, other states aren't seeing a rise in Hib -- but health officials aren't ruling it out.
"The situation in Minnesota might be isolated. It might be the beginning of a trend," Schuchat said.
The Hib vaccine shortage is expected to ease next summer, health officials said. In the meantime, arrangements are being made to ship an extra 37,000 doses to Minnesota over the next several months.
This should be enough to help ensure that enough vaccine is available for infants to receive all three primary vaccinations for Hib, Ehresmann said.
Parents of children under the age of 1 "should contact your provider and schedule an appointment. ... We want to encourage parents who have delayed or refused vaccination to reconsider," she said.
Health officials said the vaccine is safe and effective. At one time, 20,000 cases of Hib occurred in the United States each year, mostly among children under the age of 5. The bacteria was responsible for more than half of the annual meningitis cases in the U.S.
Now Hib is uncommon. Minnesota seldom has more than one or two cases a year, and many years has none, health officials said.