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Vanguard Explorer^™Fund

Supplement Dated February 26, 2019, to the Prospectus and Summary Prospectus Dated February 26, 2019

Important Change to Vanguard Explorer Fund

Kenneth L. Abrams will transition from Wellington Management Company LLP’s (Wellington Management) portion of Vanguard Explorer Fund, effective January 1, 2020. Mr. Abrams will continue to focus on other strategies he currently manages at Wellington Management. Daniel J. Fitzpatrick, who currently serves as associate portfolio manager of Wellington Management’s portion of the Fund, will remain as a manager of the Wellington Management portion of the Fund.

The Fund’s investment objective, strategies, and policies remain unchanged.

PS 24A 022019

Vanguard Explorer^™Fund

Supplement Dated February 26, 2019, to the Statement of Additional Information Dated February 26, 2019

Important Change to Vanguard Explorer Fund

Kenneth L. Abrams will transition from Wellington Management Company LLP’s (Wellington Management) portion of Vanguard Explorer Fund, effective January 1, 2020. Mr. Abrams will continue to focus on other strategies he currently manages at Wellington Management. Daniel J. Fitzpatrick, who currently serves as associate portfolio manager of Wellington Managment’s portion of the Fund, will remain as a manager of the Wellington Management portion of the Fund.

The Fund’s investment objective, strategies, and policies remain unchanged.

SAI 24A 022019