"We're very confident at this point that the kind of problem we saw in 1976 is really, really unlikely to occur this year with Guillain-Barre syndrome," Dr. Thomas Frieden, head of the Centers for Disease Control and Prevention, told reporters in a briefing in Atlanta Friday.
"Whether there are other problems with this or other vaccines or treatments only time will tell and we'll continue to monitor that very intensively."
As of Friday, there are 73 million doses of H1N1 vaccine available nationwide -- twice the number available a month ago -- with at least another 10 million doses being available in the coming weeks. Priority groups such as children and pregnant women are still priority for vaccination.
"Usually only about one out of five school kids gets vaccinated. Arkansas, Maine, Rhode Island, to name three states, tell us least half of the kids in many school districts are getting vaccinated against H1N1 influenza," Frieden said.
In addition, an increasing number of obstetricians are vaccinating their patients or at least knowing where their patients can be vaccinated, Frieden said.
"We don't know how likely a future wave of H1N1 influenza is this year, but we do know that the more people who are vaccinated, the less likely we'll have more spread in the coming months," Frieden added.
Guillain-Barre syndrome, an autoimmune disorder affecting the nervous system usually triggered by an acute infectious process, affected about 500 people who received swine flu immunizations in 1976, perhaps due to a bacterial contamination of the vaccine.