I think you are playing with fire by shorting this. You really have no idea how earth shaking this news is. In fact, you are not alone. Most investors are unaware of the significance of what Vertex announced today and that is why the stock price still has a lot of upside potential.
Agree with you, people need to be very careful shorting biotech stocks... I remember people shorting MDVN last year when it jumped about 140% (stock when from 19 to 40+) on positive 2b phase trial and now the stock is trading at the high 70's and it reached about 83 a few weeks ago, the stock never looked back... shorts need to be careful