Illumina Investor Presentation — September 2020

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© 2020 Illumina, Inc. All rights reserved.Illumina to Acquire GRAIL

Launching a New Era in

Additional Information and Where to Find It

In connection with the proposed transaction, Illumina, Inc. (the “Company”) intends to file with the SEC a registration statement on Form S -4 that will include a preliminary prospectus with respect to the Company’s

common stock and contingent value rights to be issued in the proposed transaction and a consent solicitation statement of GRA IL,Inc. (“Grail”) in connection with the proposed transaction. The Company may also

file other documents with the SEC regarding the proposed transaction. This document is not a substitute for the consent soli citation statement/prospectus or registration statement or any other document which the

Company may file with the SEC. INVESTORS AND SECURITY HOLDERS OF GRAIL ARE URGED TO READ THE REGISTRATION STATEMENT, WHICH W ILLINCLUDE THE CONSENT SOLICITATION

STATEMENT/PROSPECTUS, AND ANY OTHER RELEVANT DOCUMENTS THAT ARE FILED OR WILL BE FILED WITH THE SEC, AS WELL AS ANY AMENDMENT S OR SUPPLEMENTS TO THESE DOCUMENTS, CAREFULLY

AND IN THEIR ENTIRETY BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND RELATED M ATTERS. Investors and security holders may obtain free

copies of the registration statement on Form S -4 (when available), which will include the consent solicitation statement/prospec tus, and other documents filed with the SEC by the Company through the website

maintained by the SEC at www.sec.gov, through the Company’s Investor Relations page (investor.illumina.com) or by writing to Illumina Investor Relations, 5200 Illumina Way, San Diego, CA 92122.

No Offer or Solicitation

This communication is for informational purposes only and is not intended to and does not constitute an offer to subscribe for, buy or sell, or the solicitation of an offer to subscribe for, buy or sell, or an invitation to

subscribe for, buy or sell any securities or a solicitation of any vote or approval in any jurisdiction, nor shall there be any sale, issuance or transfer of securities in any jurisdiction in which such offer, invitation, sale

or solicitation would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. Nooffer of securities shall be made except by means of a prospectus meeting the

requirements of Section 10 of the Securities Act of 1933, as amended, and otherwise in accordance with applicable law.

Cautionary Notes on Forward- Looking Statements

This communication contains “forward- looking statements” within the meaning of the federal securities laws, including Section 27 A of the Securities Act of 1933, as amended, and Section 21E of the Securities