VB Vanguard Small Cap

Supplement to the Prospectuses and Summary Prospectuses for Investor Shares and Admiral™ Shares

New Target Indexes

Effective immediately, Vanguard Value Index Fund, Vanguard Growth Index Fund, Vanguard Mid-Cap Value Index Fund, Vanguard Mid-Cap Growth Index Fund, Vanguard Small-Cap Value Index Fund, and Vanguard Small-Cap Growth Index Fund have begun tracking new target indexes, as previously approved by the Funds’ board of trustees. The board believes that the new indexes, listed on the following page, are well-constructed and offer comprehensive coverage of the Funds’ respective market segments. In addition, Vanguard’s agreement with the new index provider may result in considerable savings to shareholders over time in the form of lower expense ratios.

Each new index measures the same market segment as the corresponding previous index, so the investment objectives and risks described in each Fund’s current prospectus will not change. A Fund’s new target index could provide different investment returns (either lower or higher) or different levels of volatility from those of the previous index.

Prospectus and Summary Prospectus Text Changes for Vanguard Value Index Fund

The paragraph under “Primary Investment Strategies” is replaced with the following:

The Fund employs an indexing investment approach designed to track the performance of the CRSP US Large Cap Value Index, a broadly diversified index predominantly made up of value stocks of large U.S. companies. The Fund attempts to replicate the target index by investing all, or substantially all, of its assets in the stocks that make up the Index, holding each stock in approximately the same proportion as its weighting in the Index.

The paragraph under “Annual Total Returns” is replaced with the following:

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund’s Investor Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the share classes presented compare with those of a relevant market index and other comparative indexes, which have investment characteristics similar to those of

the Fund. Keep in mind that the Fund’s past performance (before and after taxes) does not indicate how the Fund will perform in the future. Updated performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

The following credit line is added:

Vanguard funds are not sponsored, endorsed, sold, or promoted by the University of Chicago or its Center for Research in Security Prices, and neither the University of Chicago nor its Center for Research in Security Prices makes any representation regarding the advisability of investing in the funds.

Prospectus and Summary Prospectus Text Changes for Vanguard Growth Index Fund

The paragraph under “Primary Investment Strategies” is replaced with the following:

The Fund employs an indexing investment approach designed to track the performance of the CRSP US Large Cap Growth Index, a broadly diversified index predominantly made up of growth stocks of large U.S. companies. The Fund attempts to replicate the target index by investing all, or substantially all, of its assets in the stocks that make up the Index, holding each stock in approximately the same proportion as its weighting in the Index.

The paragraph under “Annual Total Returns” is replaced with the following:

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund’s Investor Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the share classes presented compare with those of a relevant market index and other comparative indexes, which have investment characteristics similar to those of the Fund. Keep in mind that the Fund’s past performance (before and after taxes) does not indicate how the Fund will perform in the future. Updated performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

The following credit line is added:

Vanguard funds are not sponsored, endorsed, sold, or promoted by the University of Chicago or its Center for Research in Security Prices, and neither the University of Chicago nor its Center for Research in Security Prices makes any representation regarding the advisability of investing in the funds.

Prospectus and Summary Prospectus Text Changes for Vanguard Mid-Cap Value Index Fund

The paragraph and table under “Fees and Expenses” is replaced with the following:

In the same section, under “Examples,” the table illustrating hypothetical expenses is restated as follows:

The paragraph under “Primary Investment Strategies” is replaced with the following:

The Fund employs an indexing investment approach designed to track the performance of the CRSP US Mid Cap Value Index, a broadly diversified index of value stocks of mid-size U.S. companies. The Fund attempts to replicate the target index by investing all, or substantially all, of its assets in the stocks that make up the Index, holding each stock in approximately the same proportion as its weighting in the Index.

The paragraph under “Annual Total Returns” is replaced with the following:

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund’s Investor Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the share classes presented compare with those of a relevant market index, which has investment characteristics similar to those of the Fund. Keep in mind that the Fund’s past performance (before and after taxes) does not indicate how the Fund will perform in the future. Updated performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

The following credit line is added:

Vanguard funds are not sponsored, endorsed, sold, or promoted by the University of Chicago or its Center for Research in Security Prices, and neither the University of Chicago nor its Center for Research in Security Prices makes any representation regarding the advisability of investing in the funds.

Prospectus and Summary Prospectus Text Changes for Vanguard Mid-Cap Growth Index Fund

The paragraph under “Primary Investment Strategies” is replaced with the following:

The Fund employs an indexing investment approach designed to track the performance of the CRSP US Mid Cap Growth Index, a broadly diversified index of growth stocks of mid-size U.S. companies. The Fund attempts to replicate the target index by investing all, or substantially all, of its assets in the stocks that make up the Index, holding each stock in approximately the same proportion as its weighting in the Index.

The paragraph under “Annual Total Returns” is replaced with the following:

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund’s Investor Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the share classes presented compare with those of a relevant market index, which has investment characteristics similar to those of the Fund. Keep in mind that the Fund’s past performance (before and after taxes) does not indicate how the Fund will perform in the future. Updated performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

The following credit line is added:

Vanguard funds are not sponsored, endorsed, sold, or promoted by the University of Chicago or its Center for Research in Security Prices, and neither the University of Chicago nor its Center for Research in Security Prices makes any representation regarding the advisability of investing in the funds.

Prospectus and Summary Prospectus Text Changes for Vanguard Small-Cap Value Index Fund

The paragraph and table under “Fees and Expenses” is replaced with the following:

The paragraph under “Primary Investment Strategies” is replaced with the following:

The Fund employs an indexing investment approach designed to track the performance of the CRSP US Small Cap Value Index, a broadly diversified index of value stocks of small U.S. companies. The Fund attempts to replicate the target index by investing all, or substantially all, of its assets in the stocks that make up the Index, holding each stock in approximately the same proportion as its weighting in the Index.

The paragraph under “Annual Total Returns” is replaced with the following:

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund’s Investor Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the share classes presented compare with those of a relevant market index and other comparative indexes, which have investment characteristics similar to those of the Fund. Keep in mind that the Fund’s past performance (before and after taxes) does not indicate how the Fund will perform in the future. Updated performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

The following credit line is added:

Vanguard funds are not sponsored, endorsed, sold, or promoted by the University of Chicago or its Center for Research in Security Prices, and neither the University of Chicago nor its Center for Research in Security Prices makes any representation regarding the advisability of investing in the funds.

Prospectus and Summary Prospectus Text Changes for Vanguard Small-Cap Growth Index Fund

The paragraph under “Primary Investment Strategies” is replaced with the following:

The Fund employs an indexing investment approach designed to track the performance of the CRSP US Small Cap Growth Index, a broadly diversified index of growth stocks of small U.S. companies. The Fund attempts to replicate the target index by investing all, or substantially all, of its assets in the stocks that make up the Index, holding each stock in approximately the same proportion as its weighting in the Index.

The paragraph under “Annual Total Returns” is replaced with the following:

The following bar chart and table are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund’s Investor Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the share classes presented compare with those of a relevant market index and other comparative indexes, which have investment characteristics similar to those of the Fund. Keep in mind that the Fund’s past performance (before and after taxes) does not indicate how the Fund will perform in the future. Updated performance information is available on our website at vanguard.com/performance or by calling Vanguard toll-free at 800-662-7447.

The following credit line is added:

Vanguard funds are not sponsored, endorsed, sold, or promoted by the University of Chicago or its Center for Research in Security Prices, and neither the University of Chicago nor its Center for Research in Security Prices makes any representation regarding the advisability of investing in the funds.

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Vanguard funds are not sponsored, endorsed, sold, or promoted by the University of Chicago or its Center for Research in Security Prices, and neither the University of Chicago nor its Center for Research in Security Prices makes any representation regarding the advisability of investing in the funds.