Amendment: SEC Form SCHEDULE 13G/A filed by Sotera Health Company

Warburg Pincus Reporting Persons is 450 Lexington Avenue, New York, New York 10017

See Item 2(a).

The information required by Items 4(a)-(c) is set forth in Rows 5-11 of the cover page hereto for each Warburg Pincus Reporting Person and is incorporated herein by reference for each such Warburg Pincus Reporting Person. On November 19, 2020, (i) the Issuer, (ii) Warburg Pincus Private Equity XI, L.P., Warburg Pincus Private Equity XI_B, L.P., Warburg Pincus Private Equity XI-C, L.P., WP XI Partners, L.P. and Bull Co-Invest (collectively, the "Warburg Pincus Sponsors"), (iii) GTCR Fund XI/A LP, GTCR Fund XI/C LP, and GTCR Co-Invest XI LP. (collectively, the "GTCR Funds") and (iv) certain other holders of Common Stock of the issuer ( the "Other Investors"), entered into a Stockholders Agreement (the "Stockholders Agreement"). The Stockholders Agreement sets forth certain governance arrangements with respect to the Issuer, transfer restrictions on Other Investors and indemnification matters. Pursuant to the Stockholders Agreement, each of the Warburg Pincus Sponsors and the GTCR Funds has agreed to vote the shares of Common Stock of the Issuer that each holds of record in a certain manner on matters related to the election of certain directors appointed by the Warburg Pincus Sponsors and the GTCR Sponsors. The Warburg Pincus Sponsors and the GTCR Sponsors hold an aggregate total of 103,038,253 shares of Common Stock of the Issuer (approximately 36.3% of the outstanding shares of Common Stock of the Issuer), including 41,215,301 shares of Common Stock of the Issuer that are publicly reported as being owned by the GTCR Sponsors and 61,822,952 shares of Common Stock of the Issuer that are publicly reported as being owned by the Warburg Pincus Reporting Persons. The Warburg Pincus Reporting Persons are not entitled to any rights as a shareholder of the Issuer with respect to the shares of Common Stock of the Issuer beneficially owned by the Other Investors or the GTCR Sponsors except as expressly set forth in the Stockholders Agreement and the Warburg Pincus Reporting Persons do not have dispositive power over the Common Stock owned by the GTCR Sponsors. Each Warburg Pincus Reporting Person expressly disclaims beneficial ownership (within the meaning of Rule 13d-3 of the Exchange Act) with respect to any shares of Common Stock of the Issuer other than the shares of Common Stock of the Issuer owned of record by such Warburg Pincus Reporting Person. The number of shares of Common Stock of the Issuer owned by each Warburg Pincus Reporting Person as set forth in Rows 5 - 11 of their respective cover pages to this Schedule 13G does not reflect the aggregate shares of Common Stock of the Issuer owned by the Other Investors. The aggregate total of 41,215,301 shares of Common Stock of the Issuer indicated in this Amendment No. 2 to Schedule 13G as being beneficially owned by the GTCR Sponsors is derived from the GTCR Sponsors' Form 4, filed with the Commission on September 9, 2025, and is not purported to be an accurate representation of the GTCR Sponsors' beneficial ownership as of the date of this Amendment No. 2 to Schedule 13G. The GTCR Sponsors are responsible for reporting their beneficial ownership of shares of Common Stock of the Issuer on their own behalf, and the Warburg Pincus Reporting Persons disclaim responsibility for reporting the shares of Common Stock of the Issuer beneficially owned by the GTCR Sponsors.

The percentages used herein are calculated based on 284,046,606 shares of Common Stock outstanding as of July 29, 2025 as reported on the Issuer's final prospectus reported on Form 424B7, filed on September 3, 2025.

0.00

103,038,253

0.00

61,822,952

Other than as set forth herein, no other person has the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, in excess of 5% of the total outstanding Common Stock.

(1) The Warburg Pincus Reporting Persons are making this single, joint filing because they may be deemed to constitute a "group" within the meaning of the Exchange Act. The joint filing agreement among the Warburg Pincus Reporting Persons to file this Amendment No. 2 to Schedule 13G jointly in accordance with Rule 13d-1(k) of the Exchange Act is incorporated by reference as Exhibit 99.1. (2) Each Warburg Pincus Reporting Person expressly disclaims beneficial ownership (within the meaning of Rule 13d-3 of the Exchange Act) with respect to any shares of Common Stock of the Issuer other than the shares of Common Stock of the issuer owned of record by such Warburg Pincus Reporting Person.