Sec Form 4 Filing - Blaser Brian J @ Quanterix Corp - 2023-01-06

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Blaser Brian J 2. Issuer Name and Ticker or Trading Symbol Quanterix Corp [ QTRX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O QUANTERIX CORPORATION, 900 MIDDLESEX TURNPIKE 3. Date of Earliest Transaction (MM/DD/YY) 01/06/2023 (Street) BILLERICA, MA01821 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 01/06/2023 A 16,102( 1 ) A $ 0 16,102( 2 ) D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Stock Option (right to buy) $ 12.94 01/06/2023 A 24,153 ( 3 ) 01/06/2033 Common Stock 24,153 $ 0 24,153 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Blaser Brian J C/O QUANTERIX CORPORATION 900 MIDDLESEX TURNPIKE BILLERICA, MA01821 X Signatures /s/ Brian Keane, as Attorney-in-Fact 01/09/2023 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Represents shares of stock issuable on vesting of restricted stock units. The restricted stock units vest as to one-third of shares on each of January 6, 2024, January 6, 2025 and January 6, 2026. ( 2 )Includes 16,102 restricted stock units. ( 3 )The option vests as to one-third of the shares on January 6, 2024, and the remaining two-thirds of the shares vest monthly thereafter over two years in 24 successive equal installments.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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