Mutual Fund Summary Prospectus (497k)

Vanguard Mid-Cap Index Fund

Summary Prospectus

April 12, 2013

Signal ^® Shares for Participants

Vanguard Mid-Cap Index Fund Signal Shares (VMISX)

The Fund’s statutory Prospectus and Statement of Additional Information dated

April 12, 2013, are incorporated into and made part of this Summary Prospectus

by reference.

Before you invest, you may want to review the Fund’s Prospectus, which

contains more information about the Fund and its risks. You can find

the Fund’s Prospectus and other information about the Fund online at

www.vanguard.com/prospectus . You can also get this information at no

cost by calling 800-523-1188 or by sending an e-mail request to

online@vanguard.com.

The Securities and Exchange Commission (SEC) has not approved or disapproved these securities or

passed upon the adequacy of this prospectus. Any representation to the contrary is a criminal offense.

Vanguard Mid-Cap Index Fund

Investment Objective

The Fund seeks to track the performance of a benchmark index that measures the investment return of mid-capitalization stocks.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Signal Shares of the Fund.


Shareholder Fees
(Fees paid directly from your investment)

Sales Charge (Load) Imposed on Purchases	None
Purchase Fee	None
Sales Charge (Load) Imposed on Reinvested Dividends	None
Redemption Fee	None

Annual Fund Operating Expenses

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


Management Expenses	0.07%
12b-1 Distribution Fee	None
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.10%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Signal Shares with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you invest $10,000 in the Fund’s shares. This example assumes that the Shares provide a return of 5% a year and that total annual fund operating expenses remain as stated in the preceding table. The results apply whether or not you redeem your investment at the end of the given period. 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
$10	$32	$56	$128

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in more taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the previous expense example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 17%.

Primary Investment Strategies

The Fund employs an indexing investment approach designed to track the performance of the CRSP US Mid Cap Index, a broadly diversified index of 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.

Primary Risks

An investment in the Fund could lose money over short or even long periods. You should expect the Fund’s share price and total return to fluctuate within a wide range, like the fluctuations of the overall stock market. The Fund is subject to the following risks, which could affect the Fund’s performance:

• Stock market risk , which is the chance that stock prices overall will decline. Stock markets tend to move in cycles, with periods of rising prices and periods of falling prices. The Fund’s target index may, at times, become focused in stocks of a particular sector, category, or group of companies, which could cause the Fund to underperform the overall stock market.

• Investment style risk , which is the chance that returns from mid-capitalization stocks will trail returns from the overall stock market. Historically, mid-cap stocks have been more volatile in price than the large-cap stocks that dominate the overall market, and they often perform quite differently.

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Annual Total Returns

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 Signal Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns 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 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.

Annual Total Returns — Vanguard Mid-Cap Index Fund Signal Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 21.54% (quarter ended September 30, 2009), and the lowest return for a quarter was –25.62% (quarter ended December 31, 2008).


Average Annual Total Returns for Periods Ended December 31, 2012

			Since
			Inception
			(Mar. 30,
	1 Year	5 Years	2007)
Vanguard Mid-Cap Index Fund Signal Shares	16.02%	3.15%	3.00%
MSCI US Mid Cap 450 Index
(reflects no deduction for fees or expenses)	16.04%	3.19%	3.03%

Investment Advisor
The Vanguard Group, Inc.

Portfolio Manager

Donald M. Butler, CFA, Principal of Vanguard. He has managed the Fund since its inception in 1998.

Tax Information

The Fund’s distributions will be reinvested in additional Fund shares and accumulate on a tax-deferred basis if you are investing through an employer-sponsored retirement or savings plan. You will not owe taxes on these distributions until you begin withdrawals from the plan. You should consult your plan administrator, your plan’s Summary Plan Description, or your tax advisor about the tax consequences of plan withdrawals.

Payments to Financial Intermediaries

The Fund and its investment advisor do not pay financial intermediaries for sales of Fund shares.

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Vanguard Mid-Cap Index Fund Signal Shares—Fund Number 1344

CFA ^® is a trademark owned by CFA Institute.

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.

SPI 1344 042013