| SC 13G/A | 2012-02-14 | Capital Research Global Investors | BIOGEN IDEC INC. | 14,115,300 | 5.8% | EDGAR |
| SC 13G | 2012-02-14 | FMR LLC | BIOGEN IDEC INC. | 21,092,132 | 8.7% | EDGAR |
| SC 13G/A | 2012-02-13 | BlackRock Inc. | BIOGEN IDEC INC. | 17,256,111 | 7.1% | EDGAR |
| SC 13G/A | 2012-02-13 | PRIMECAP MANAGEMENT CO/CA/ | BIOGEN IDEC INC. | 23,835,526 | 9.8% | EDGAR |
| SC 13G/A | 2012-02-13 | BIOGEN IDEC INC. | AVEO PHARMACEUTICALS INC | 0 | 0.0% | EDGAR |
| SC 13G/A | 2012-02-13 | BIOGEN IDEC INC. | SUNESIS PHARMACEUTICALS INC | 0 | 0.0% | EDGAR |
| SC 13G/A | 2012-01-27 | VANGUARD CHESTER FUNDS | BIOGEN IDEC INC. | 12,104,500 | 5.0% | EDGAR |
| SC 13G/A | 2011-11-03 | PRIMECAP MANAGEMENT CO/CA/ | BIOGEN IDEC INC. | 24,205,126 | 10.0% | EDGAR |
| SC 13D/A | 2011-06-22 | ICAHN CARL C | BIOGEN IDEC INC. | 1,645,051 | 0.7% | EDGAR |
| SC 13D/A | 2011-05-23 | ICAHN CARL C | BIOGEN IDEC INC. | 2,685,803 | 1.1% | EDGAR |
| SC 13G/A | 2011-02-14 | FMR LLC | BIOGEN IDEC INC. | 11,831,653 | 5.0% | EDGAR |
| SC 13G/A | 2011-02-14 | PRIMECAP MANAGEMENT CO/CA/ | BIOGEN IDEC INC. | 25,873,874 | 10.9% | EDGAR |
| SC 13G/A | 2011-02-11 | Clearbridge Advisors, LLC | BIOGEN IDEC INC. | 16,528,916 | 6.9% | EDGAR |
| SC 13G/A | 2011-02-11 | GOLDMAN SACHS ASSET MANAGEMENT LP | BIOGEN IDEC INC. | 8,212,605 | 3.4% | EDGAR |
| SC 13G | 2011-02-11 | BIOGEN IDEC INC. | AVEO PHARMACEUTICALS INC | 2,877,700 | 8.1% | EDGAR |
| SC 13G | 2011-02-10 | VANGUARD CHESTER FUNDS | BIOGEN IDEC INC. | 12,550,400 | 5.3% | EDGAR |
| SC 13G | 2011-02-09 | Capital Research Global Investors | BIOGEN IDEC INC. | 20,882,384 | 8.8% | EDGAR |
| SC 13G/A | 2011-02-02 | BlackRock Inc. | BIOGEN IDEC INC. | 13,504,437 | 5.7% | EDGAR |
| SC 13G/A | 2010-08-10 | PRIMECAP MANAGEMENT CO/CA/ | BIOGEN IDEC INC. | 26,339,229 | 10.9% | EDGAR |
| SC 13D/A | 2010-03-22 | ICAHN CARL C | BIOGEN IDEC INC. | - | - | EDGAR |