"Right now the recommendations are to make sure all children get the primary vaccine series, and providers should defer giving the booster dose until the vaccine supply increases," Jackson said. "We are not worried about sudden increases in Hib disease, but we are worried over time that, not having the booster, we could start to see increases in Hib," he said.
The agency is asking doctors, state health departments and state laboratories to increase their surveillance of Hib.
Jackson said tracking Hib cases isn't easy. There are many different types of influenzae and there are many steps involved in testing and reporting the various types, so information often gets lost along the way, he said.
"The information we are getting at CDC is that we are missing about 40 percent of cases," Jackson said. "That's a little worrisome because that's 40 percent of people we don't know if they have type b, which is the vaccine-preventable one, the one we are really worried about, or if they have something else. It makes it harder for us to see changes in Hib if there really is something going on in the population."
Dr. Marc Siegel, an associate professor of medicine at New York University School of Medicine, said parents shouldn't panic because of the vaccine shortage.
"There used to be 20,000 cases a year, but the vaccine has brought it to less than 100," Siegel said. "The numbers remain small. We've almost stamped this thing out with the vaccine, so don't assume your kid is going to get it."
For more on Hib disease, visit the CDC.
SOURCES: Michael Jackson, Ph.D., epidemiologist, U.S. Centers for Disease Control and Prevention, Atlanta;
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