While the number of AE reports and the reporting rate were higher for the H1N1 vaccine than for the 2009-10 seasonal vaccine, the researchers write, “These findings, however, should be interpreted in light of the publicity around the 2009 H1N1 vaccine and efforts to increase reporting to VAERS. Heightened public awareness and stimulated reporting likely enhanced reporting to VAERS.
“Furthermore, although 2009-H1N1 was licensed similarly to seasonal influenza vaccines, it was likely perceived as a ‘new’ vaccine by the public and susceptible to the known tendency (i.e., the Weber effect) for adverse events to be reported more frequently following newly licensed products.”
The report adds that many efforts were made to boost AE reports for the pandemic vaccine, including providing an information card to vaccinees that included VAERS reporting information. As a result, the VAERS Web site received three times as many visits in the 2009-10 season as in past seasons.
The authors also comment that the fairly consistent reporting of AEs for the H1N1 vaccine compared with the seasonal vaccine among all age-groups and for both serious and nonserious events “argues against an association between [the] vaccine and a particular adverse outcome.”