Officials at the U.S. Food and Drug Administration don't know if the more than 100 new cases of strange behavior, including three deaths from falls, are tied to the drug, to the flu itself, or a combination of both, the Associated Press reported.
The FDA is mulling changes to the Tamiflu label that may recommend that all patients, especially children, be closely monitored while on the drug.
The agency acknowledged that stopping Tamiflu treatment might harm flu patients if the virus is the underlying cause of delirium, hallucinations and other abnormal behavior that make up the symptoms observed in children abroad. Many of the pediatric problems have been reported in Japan, where the number of Tamiflu prescriptions is about 10 times greater than in the United States, the AP said.
Although severe cases of flu have been known to produce such side effects, the number and type of cases, plus comments from doctors who believe the abnormal behavior is associated with the drug, are keeping the FDA from ruling out Tamiflu as the cause.
The FDA's pediatric advisory committee is to discuss the label recommendation on Thursday, the AP said. The FDA typically follows the advice of its advisory panels.
Also on Monday, the U.S. Centers for Control and Prevention said that, despite delays in the distribution of seasonal flu vaccine this year, the agency is confident that enough doses of vaccine will be available over the next few weeks to meet any demand.
In October, the CDC said that while there was no shortage of vaccine this year, there were going to be delays in getting all the doses manufactured and distributed. The problem particularly affects children's doses.
Since these are delays, not shortages, CDC Director Dr. Julie Gerberding said she's encouraging people to get vaccinated even as late as early January.
"It's the beginning of the flu season," Gerberding said during a teleconference. "As always, flu is unpredictable, so we are not going to be able to say how fast it's going to evolve, where it will hit next, or how bad it will be."
Cases of flu have already been reported in Arizona and California. Usually, the flu season peaks in late January or February.
Gerberding noted that this year's supply of vaccine is the largest ever produced in the United States. "We are still projecting between 110 million and 115 million doses," she said. So far, about 77 million doses have been distributed.
In all, 210 million Americans are eligible for flu shots, Gerberding said, including children between 6 months and 5 years of age.
Although the total number of vaccine doses is the largest ever, there are areas of the country experiencing shortages. "There are certain providers and health agencies that are having trouble getting their doses," Gerberding said. "There are still mismatches between the need and the supply."
Gerberding noted that these delays are out of the CDC's hands. "These are private-sector problems," she said.
The CDC is participating in a national influenza vaccine drive to encourage people to get vaccinated whenever vaccine is available. "It is never too late to get your flu shot," Gerberding said. Moreover, getting vaccinated is the best way to protect yourself from the flu, she added.
At the teleconference, Dr. John Agwunobi, assistant secretary for health at the U.S. Department of Health and Human Services, said people could get vaccinated as late as early January.
Dr. L.J. Tan, a spokesman for the American Medical Association, said, "We know that there are substantial medical benefits to receiving the vaccine after Thanksgiving and beyond. It is often mistakenly believed that the only time to get the vaccine is before Thanksgiving."
Gerberding acknowledged that many parents are concerned about the addition of thimerosal to the flu vaccine. Thimerosal, a mercury compound used as a preservative, is suspected by some be at least partly responsible for the growing number of autism cases among children.
"Children can have very serious disease from influenza," Gerberding said. "The flu shot is the best way to protect them, there's no doubt about that. Concerns about thimerosal are on the minds of many parents. We have not been able to identify any data that indicates a flu shot poses any risk associated with thimerosal."
The CDC chief believes the benefits of vaccination are too important to ignore. "If you are balancing the benefit of immunization with what is an unknown or no-risk situation from thimerosal, it seems clear to me what needs to be done," Gerberding said. "That's why we in the public-health community are encouraging parents to get their kids vaccinated. The risk of flu far outweighs any theoretical complications from the vaccine."
In related news, a study in the Nov. 13 issue of the Archives of Internal Medicine finds that the flu vaccine slightly increases the risk of Guillain-Barre syndrome, which occurs when the body's immune system attacks part of the nervous system, resulting in tingling or weakness and possible paralysis.
"This study has findings that are consistent with findings that were published a few years ago," Gerberding said. "These findings indicate that there is an increased risk of about one in a million of Guillain-Barre syndrome cases among those who are vaccinated, compared to those who are not vaccinated. But when we compare the risks associated with influenza infection with the risk of Guillain-Barre syndrome, we see that the risk of not being vaccinated far outweighs the risk for Guillain-Barre syndrome," she said.
One expert thinks the flu vaccine is safe and effective, and that thimerosal is not really a problem, compared with the potential consequences of flu.
"We have environmental concerns, but to put it all on thimerosal based on an unproven association is really the wrong way to go," said Dr. Marc Siegel, a clinical associate professor of medicine at New York University School of Medicine, and author of Bird Flu: Everything You Need to Know About the Next Pandemic. "I am satisfied that there has never been an association shown between thimerosal and autism."
Each year in the United States, as much as 20 percent of the population can get the flu, more than 200,000 people are hospitalized from flu complications, and about 36,000 people die from the disease, according to the CDC.
source - HealthDay