H1N1 vaccine study investigating hints of complications from vaccine
Saturday, April 24, 2010
Federal health officials are investigating the first hints of any possible significant complications from the H1N1 vaccine, but stressed that the concerns will probably turn out to be a false alarm.
The latest analysis of data has detected what could be a somewhat elevated rate of Guillain-Barré syndrome, which can cause paralysis and death; Bell's palsy, a temporary facial paralysis; and thrombocytopenia, which is a low level of blood platelets, officials reported Friday. The data is being collected through five of the networks the government is using to monitor people who were inoculated against the swine flu.
Officials stressed that it is far too early to know whether the vaccine was increasing the risk of those conditions or whether there is some other explanation, such as doctors identifying more cases because of the intensive effort to pinpoint any safety problems with the vaccine.
Based on the preliminary report, the Health and Human Services Department's National Vaccine Advisory Committee, which has been charged with monitoring the vaccine's safety, voted unanimously to follow up on the findings. "We're at the first step of determining whether there is a problem," Guthrie S. Birkhead, who chairs the committee, said during a teleconference in which a subcommittee of experts presented its latest findings on the data. "There's a lot more work to determine whether there is."
Marie McCormick, who led the subcommittee, said there was a good chance the indications of problems could disappear with further analysis. Even if the link with Guillain-Barrésyndrome is confirmed, the committee calculated the vaccine at most could be causing one extra case per 1 million people vaccinated.
"We have categorized this as a potential, not even a weak, signal," McCormick said, adding that no signs of problems have been seen in the other networks of data the government has been analyzing.
Even if the possible risks turn out to be real, officials stressed that the danger of the flu remains far greater.
"From everything we know right now, the influenza vaccine, including the H1N1 vaccine, is very safe, and it's much riskier to get influenza than the influenza vaccine," said Anne Schuchat of the federal Centers for Disease Control and Prevention.
Officials said they were not surprised that some possible problems that turn out to be false alarms might be found, given how intensively the vaccine's safety is being monitored.
The vaccine was administered to 350 million to 400 million people worldwide, including as many as 80 million Americans, as part of an unprecedented response to the first flu pandemic in decades.
Since the inoculation program was launched, health officials have been particularly concerned about Guillain-Barré syndrome, in part because a vaccine made in 1976 in response to a different strain of H1N1 influenza led to a small increase in the number of cases of the condition.
But officials expressed confidence that the new vaccine is safe because it was produced with the same methods employed since then to make the seasonal flu vaccine, which has been administered safely to millions of people.
Each year, about 3,000 to 6,000 people in the United States develop Guillain-Barré syndrome whether or not they were vaccinated -- a rate of one to two people out of every 100,000 people. Some studies have indicated that the seasonal flu vaccine might be associated with one additional case of the syndrome out of 1 million vaccinated. And influenza itself can cause the syndrome.
Although the vaccine was produced in record time, antiquated technology and unexpected problems growing the virus fast enough to produce the vaccine meant that most of the doses did not arrive until after the second wave of infections peaked last fall. That led to widespread anxiety, frustration and lines across the country as people scrambled to find the first doses. By the time most of the vaccine was ready, the second wave was already receding and demand fell sharply, leaving millions of doses unused.
The relatively low number of deaths compared with previous pandemics and the millions spent on the vaccine have led to charges that the World Health Organization exaggerated the pandemic's risks. That prompted the Geneva-based arm of the United Nations to launch two investigations, which are ongoing.