The Centers for disease control (CDC) released safety data on the current season H1N1 monovalent vaccine. Based on data collected a total of 82 adverse events were reported per million doses. This is in comparison to 47 cases per million doses seen in the seasonal influenza vaccine. At first this may seem much higher but the proportion of serious adverse effects was about the same.
Of the 3,783 adverse events reported in the 438,376 doses monitored, 204 adverse effects were categorized as serious (ending in death, hospitalization, disability) similarly 283 serious events were reported for seasonal influenza vaccination.
Of the 13 deaths that were reported nine had underlying illneses. One death occurred after a motor vehicle accident. There were no common conditions or causes of death in the 13 deaths.
With regards to Guillain Barre there were a total of twelve possible cases were reported. Of these only 4 actually met the definition of Guillain Barre.
Overall the number of adverse effects appear to be few and most of them of minor consequences. This is similar to the data published in the New England Journal of Medicine earlier. There are of course limitations in the data especially not being able to detect very rare associations but they will be after all “very rare”.
The healthcare community especially has done a remarkable job with H1N1 given the short time available to mount a response to the impending threat.