Parents urged to make sure infants are vaccinated against Hib
A resurgence in the childhood infectious disease Hib (Haemophilus influenza type B) in Minnesota in 2008 has prompted state health officials to obtain additional vaccine and urge parents to work with their health care providers to make sure infants are getting the recommended primary series of three doses of Hib vaccine.
Five cases of Hib were reported in the state in 2008, according to the Minnesota Department of Health.
Three of the five cases, including one death, occurred in unimmunized children. One case occurred in a child too young to complete the primary series and another case occurred in a child who had received the primary series, but was later found to have an underlying condition.
"We have not seen this number of cases in young children since 1992," said Dr. Ruth Lynfield, state epidemiologist. "It is extremely sad to see this disease resurface, resulting in very severe illness including meningitis and death. These cases underscore the importance of maintaining high vaccination rates."
Hib is a severe bacterial infection that occurs most often in infants, but also in young children and usually requires hospitalization.
Hib infection can result in serious and sometimes fatal illnesses such as meningitis, bloodstream infection, epiglottitis (severe swelling of the tissue of the throat resulting in breathing difficulty), pneumonia, bone or joint infections.
A national shortage of Hib vaccine has existed since November 2007 and is expected to last into mid-2009. During the vaccine shortage, national advisory groups recommended that health care providers defer giving a fourth and final booster dose of Hib vaccine to toddlers, age 12-15 months so that as many infants as possible could complete the primary series.
Minnesota health officials have found that in addition to deferral of the booster dose, the shortage has resulted in fewer infants receiving the primary series. The department's findings were reported today in a special dispatch edition of MMWR, a weekly report by the Centers for Disease Control.
While the plan to defer the booster dose to assure infant vaccination seems to be working in most other states, it's not in Minnesota.
In part, this may be because a greater percentage of providers in Minnesota have traditionally used the vaccine produced by Merck, which is the one in shortest supply, thus exacerbating the problem in Minnesota.
"Recent data on Minnesota's immunization rates during the Hib vaccine shortage show that fewer infants are getting a third dose than we would normally expect," said Kristen Ehresmann, immunizations program manager for MDH. "As many as 18 percent fewer infants at seven months were getting the third dose of Hib compared with the two other vaccines given at age 6 months. The decrease in the level of Hib immunization results in a drop in "herd immunity", where unimmunized and under-immunized children are vulnerable to Hib disease.
MDH officials have worked with CDC and vaccine manufacturer Sanofi-Pasteur to make additional doses of Hib vaccine available in Minnesota. Over the next several months, Minnesota will receive an additional 37,000 doses from CDC and Sanofi.
"Since we are seeing a resurgence of Hib disease, it's important for parents of infants to work with their health care provider or clinic to make sure their baby has received three doses of Hib vaccine," Ehresmann said. "If your child hasn't received all three Hib shots, schedule additional visits as soon as possible."
"Some parents have read information that encourages them to refuse or delay vaccinations for their child. However, this puts their children and other children at risk for serious diseases, such as Hib," Ehresmann said.
Hib vaccine became available for use in infants in 1991. Before vaccine, 20,000 cases of Hib occurred every year in the U.S., mostly among children under five years old. After the widespread use of vaccine, Minnesota rarely recorded more than 1 or 2 cases of Hib a year, often none.
Before vaccine was available, Hib accounted for 50-60 percent of all cases of meningitis in the U.S. Of these, 2-5 percent died and 15-30 percent experienced lasting brain damage or deafness.
Parents who have questions about their child's vaccination status should talk to their health care provider.
More information on Haemophilus influenzae type-b and the vaccine can be found on the MDH Web site at www.health.state.mn.us/divs/idepc/diseases/hib/index.html .