X0306 4 2021-12-31 0 0001604477 SQZ Biotechnologies Co SQZ 0001517214 Knopf Lawrence J 200 ARSENAL YARDS BLVD WATERTOWN MA 02472 0 1 0 0 General Counsel Common Stock 2021-12-31 5 A 0 E 454 7.5905 A 454 D The reporting person is voluntarily reporting the acquisition on December 31, 2021 of 454 shares of the issuer's common stock pursuant to the issuer's employee stock purchase plan. /s/ Lawrence J. Knopf 2022-01-04