The H1N1 influenza pandemic of 2009 was the second pandemic in recent history that resulted from the H1N1 influenza virus, also known as the swine flu. The first one, known as the 1918 flu pandemic, killed over 50 million people, or about 1-3% of the world’s population at the time. The 2009 pandemic, though not as serious as the one in 1918, probably killed over 500 thousand people worldwide. In the United States, the CDC estimated that between 43 and 89 million people were infected with the 2009 H1N1 flu. They also estimated that of those, about 200-400 thousand were hospitalized, and approximately 12,470 died. The only reason the pandemic wasn’t worse was probably as a result of an effective H1N1 vaccine along with a broad effort to vaccinate those at highest risk of complications.
Along with the vaccination program, comprehensive safety surveillance was initiated to monitor for adverse events. This program identified a small increase in Guillain-Barré syndrome following the H1N1 vaccination. In paper published this week, researchers did a meta-analysis of the data from the monitoring program to quantify the level of risk. Continue reading “Slight risk of Guillain-Barré syndrome after H1N1 flu vaccination”