WEDNESDAY, Feb. 2, 2011 (HealthDay News) -- Close to 100 million doses of H1N1 flu vaccine were given out in 2009-2010 in China, with no pattern of serious side effects observed, a review by Chinese scientists finds.
Moreover, no evidence surfaced that the swine flu vaccine, as it was called, increased the risk for Guillain-Barre syndrome, according to the report published in the Feb. 2 online edition of the New England Journal of Medicine.
An outbreak of Guillain-Barre around the time of widespread vaccination against swine flu in 1976-1977 led some to blame the vaccine for the disease. In Guillain-Barre, the body's immune system attacks the nervous system causing muscle weakness and paralysis.
Back then, some 1,000 cases of Guillain-Barre syndrome were reported, about half in people vaccinated. Hypothetically, a case could have been made that they were a reaction to the H1N1 antigen in the vaccine, said flu expert Dr. Marc Siegel, an associate professor of medicine at New York University in New York City.
Some concerns surfaced about the safety of the H1N1 vaccine recommended in 2009-2010 against the H1N1 pandemic.
But this study clearly shows that last year's H1N1 vaccine was not associated with increases in Guillain-Barre syndrome, Siegel said.
"If anybody still thinks that pig viruses cause Guillain-Barre at an increased rate, this study shows that's not the case," he said.
Noting that this year's seasonal flu vaccine contains last year's H1N1 vaccine, Siegel said, "there is no reason to be concerned that this antigen is in the current vaccine."
For the study, a team led by Dr. Yu Wang, from the Chinese Center for Disease Control and Prevention's National Immunization Program in Beijing, collected data on any adverse effects from the vaccine from doctors throughout China.
In all, 89.6 million doses of H1N1 vaccine were given from the end of September 2009 through March 2010. A total of 8,067 adverse events was reported. That's a rate of 90 adverse reactions for every million doses, the researchers noted.
However, only 6,552 of the adverse reactions proved to be related to the vaccine -- a rate of 73.1 per million doses, Wang's group said.
Among the most serious were allergic reactions, which accounted for about 13 percent of all the events. Eleven cases of Guillain-Barre syndrome were reported among those vaccinated, a rate of 0.1 per million doses, which is lower than the normal rate of the disease in China, Wang's team found.
"These findings suggest that the H1N1 vaccine has a reasonable safety profile, and there is no evidence that the vaccine is associated with an increased risk of the Guillain-Barre syndrome," the researchers concluded in their report.
Commenting on the study, Dr. Bruce Farber, chief of the Division of Infectious Diseases at North Shore University Hospital in Manhasset, N.Y., said that "as we know from the H1N1 experience in the U.S. last year, our vaccine was safe.
"Despite the initial public skepticism and some cynicism, influenza vaccines are safe and effective," he added. "The risk-benefit ratio, which is what vaccines and everything in medicine is about, is overwhelmingly in favor of vaccination."
Mild side effects were more common among children aged 9 and younger who were vaccinated than for older adults, the study found.
Each year in the United States about 36,000 people die from complications from the flu, and the vaccine is the best protection against getting the flu in the first place, according to the U.S. Centers for Disease Control and Prevention.
For more information on the flu, visit the U.S. Centers for Disease Control and Prevention.