 One MD praised that the PSI were "a big improvement over the previous guidance"; while historical influenza expert and author John M. Barry was more critical of the PSI, saying not enough emphasis was placed on basic health principles that could have an impact at the community level, adding "I'd feel a lot more comfortable with a lot more research [supporting them]".During the initial press releases in 2007, the CDC acknowledge that the PSI and the accompanying guidelines were a work in progress and will likely undergo revision in the months following their release.In 2014, after the 2009 H1N1 influenza pandemic, the PSI was replaced by the Pandemic Severity Assessment Framework, which uses quadrants based on transmissibility and clinical severity rather than a linear scale.