Safety in Numbers

A review by scientists found that of the near 90 million doses of H1N1 flu vaccine administered in 2009-2010 in China, no pattern of serious side effects has emerged.

The so-called swine flu vaccine was thought to have been linked to an outbreak of Guillain-Barre syndrome in 1976-1977. In Guillain-Barre syndrome, the immune system attacks the nervous system, resulting in muscle weakness and sometimes paralysis.

Flu expert Dr. Marc Siegel, an associate professor of medicine at New York University in New York City, said this study should rectify any misconceptions about pig viruses causing Guillain-Barre.

The study, conducted by a team led by Dr. Yu Wang from the Chinese Center for Disease Control and Prevention's National Immunization Program in Beijing, uncovered approximately 90 adverse reactions to the vaccine per every million doses. A total of 8,067 adverse reactions were recorded, but only 6,552 of these reactions turned out to be related to the vaccine -- a rate of about 73 adverse reactions per one million doses.

About 36,000 people die from flu-related complications in the United States each year, according to the US Centers for Disease Control and Prevention.