While no one can predict when the next prolonged bull move will appear, the stock market has proven time and again its ability to rebound from even the most dire periods of volatility. Vertex Pharmaceuticals (NASDAQ: VRTX) has continued to deliver gains against the backdrop of the broader volatile market over the last year, but this isn't only a testament to the typical resilience of the healthcare industry in times of economic turmoil. The company continues to rake in revenue, profits, and cash from its portfolio of cystic fibrosis medicines -- currently the only drugs on the market that target the underlying root causes of the genetic ailment.