X0306 4/A 2018-02-01 2018-02-05 0 0001293971 bluebird bio, Inc. BLUE 0001343543 Gregory Philip D C/O BLUEBIRD BIO, INC. 60 BINNEY STREET CAMBRIDGE MA 02142 0 1 0 0 Chief Scientific Officer Common Stock 2018-02-01 4 A 0 7500 0.00 A 39772 D Restricted stock units for common stock vest over a two-year period at a rate of 50% on 01/04/2019 and 50% on 01/04/2020. This Form 4 amendment is being filed to report the award of 7,500 restricted stock units which was inadvertently omitted from the original Form 4 filed by the reporting person on February 5, 2018. These shares were omitted from two Form 4s filed by the reporting person on March 5, 2018 and April 4, 2018, after the filing of this original Form 4. /s/ Jason F. Cole, Attorney-in-Fact 2018-04-11