# EDGAR Filing Document

**Accession Number:** 0001107414
**File Stem:** 0001193125-26-196004
**Filing Date:** 2026-4
**Character Count:** 4212
**Document Hash:** 37990d82a378b9d201ea26304dbd10c6
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-196004.hdr.sgml**: 20260430

**ACCESSION NUMBER**: 0001193125-26-196004

**CONFORMED SUBMISSION TYPE**: 497

**PUBLIC DOCUMENT COUNT**: 14

**FILED AS OF DATE**: 20260430

**DATE AS OF CHANGE**: 20260430

**EFFECTIVENESS DATE**: 20260430

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** STATE STREET INSTITUTIONAL INVESTMENT TRUST
- **CENTRAL INDEX KEY:** 0001107414

**ORGANIZATION NAME:**
- **EIN:** 046910804
- **STATE OF INCORPORATION:** MA
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 497
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-30810
- **FILM NUMBER:** 26922753

**BUSINESS ADDRESS:**
- **STREET 1:** ONE CONGRESS STREET
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02114
- **BUSINESS PHONE:** 6176643920

**MAIL ADDRESS:**
- **STREET 1:** ONE CONGRESS STREET
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02114

## Series and Classes Contracts Data

### State Street Income Fund (Series ID: S000071465)

---

|  |  |  |
|:---|:---|:---|
| Class Name               | Ticker Symbol | Class ID   |
| State Street Income Fund | SSASX         | C000226666 |

---

## Series and Classes Contracts Data

### State Street Income Fund (Series ID: S000071465)

| Class ID   | Class Name               | Ticker Symbol   |
|:---|:---|:---|
| C000226666 | State Street Income Fund | SSASX           |

?xml version='1.0' encoding='ASCII'? STATE STREET INSTITUTIONAL INVESTMENT TRUST

------

Filed pursuant to Rule 497(e)

File Nos. 333-30810 and 811-09819

#### State Street Institutional Investment Trust

#### State Street Income Fund
(SSASX)

*Supplement Dated April 30, 2026 to the Summary Prospectus and Prospectus,* 

*each dated January 31, 2026 as may be supplemented from time to time* 

**Effective immediately, the expenses that you pay each year as a percentage of the value of your investment (the "Annual Fund Operating Expenses") have been restated to reflect current fees. Accordingly, effective immediately, the sections in the Fund's Prospectus and Summary Prospectus titled "Fees and Expenses of the Fund" and "Example" are deleted and replaced with the following:** 

#### Fees and Expenses of the Fund
The tables below describe the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund ("Fund Shares"). **You may pay brokerage commissions and other fees to financial intermediaries which are not reflected in the tables and examples below**. More information about these and other discounts is available from your financial intermediary ("Financial Intermediary") and in the "Investing in Funds Shares" section of the Fund's Prospectus.

**Shareholder Fees** (fees paid directly from your investment)

---

| |
|:---|
| Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) |
| Maximum Deferred Sales Charge (Load) (as a percentage of the lower of the sale proceeds or the original offering price) |

---

**Annual Fund Operating Expenses**

(expenses that you pay each year as a percentage of the value of your investment)

---

| | |
|:---|:---|
|  Management Fee | 0.13% |
|  Distribution and/or Shareholder Service (12b-1) Fees | 0.0% |
|  Other Expenses<sup>1</sup> | 0.19% |
|  Acquired Fund Fees and Expenses | 0.01% |
|  Total Annual Fund Operating Expenses<sup>1</sup> | 0.33% |

---

<sup>1</sup> "Other Expenses" and "Total Annual Fund Operating Expenses" have been restated to reflect current fees 

#### Example:
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated, and then sell or hold all of your Fund Shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

---

| | | | |
|:---|:---|:---|:---|
| **1 year** | **3 years** | **5 years** | **10 years** |
| $34 | $106 | $185 | $418 |

---

#### PLEASE KEEP THIS SUPPLEMENT FOR FUTURE REFERENCE
043026SUPP1