Summary Prospectus by Investment Company - Form 497K

Vanguard Variable Insurance Funds

Equity Index Portfolio

Summary Prospectus

April 26, 2024

The Portfolio's statutory Prospectus and Statement of Additional Information dated April 26, 2024, as may be amended or supplemented, are incorporated into and made part of this Summary Prospectus by reference.

Before you invest, you may want to review the Portfolio's Prospectus, which contains more information about the Portfolio and its risks. You can find the Portfolio's Prospectus and other information about the Portfolio online at www.vanguard.com/prospectus. You can also obtain this information at no cost by calling 800-522-5555 or by sending an email request to [email protected].

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.

Investment Objective

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

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy, hold, and sell shares of the Portfolio. The expenses shown in the table and in the example that follows do not reflect additional fees and expenses associated with the annuity or life insurance program through which you invest. If those additional fees and expenses were included, overall expenses would be higher.

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

Management Fees	0.13 %
12b-1 Distribution Fee	None
Other Expenses	0.01 %
Total Annual Portfolio Operating Expenses	0.14 %

Example

The following example is intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. It illustrates the hypothetical expenses that you would incur over various periods if you were to invest $10,000 in the Portfolio's shares. This example assumes that the Portfolio provides a return of 5% each year and that total annual portfolio operating expenses remain as stated in the preceding table. You would incur these hypothetical expenses whether or not you were to 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
$14	$45	$79	$179

Portfolio Turnover

The Portfolio 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. These costs, which are not reflected in annual portfolio operating expenses or in the previous expense example, reduce the Portfolio's performance. During the most recent fiscal year, the Portfolio's turnover rate was 5% of the average value of its portfolio.

Principal Investment Strategies

Vanguard Variable Insurance Funds Equity Index Portfolio (the Equity Index Portfolio) employs an indexing investment approach designed to track the performance of the Standard & Poor's 500 Index (the Index), a widely recognized benchmark of U.S. stock market performance that is dominated by the stocks of large U.S. companies. The Portfolio 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.

Principal Risks

An investment in the Portfolio could lose money over short or long periods of time. You should expect the Portfolio's share price and total return to fluctuate within a wide range. The Portfolio is subject to the following risks, which could affect the Portfolio'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 Portfolio's target index tracks a subset of the U.S. stock market, which could cause the Portfolio to perform differently from the overall stock market. In addition, the Portfolio's target index may, at times, become focused in stocks of a particular market sector, which would subject the Portfolio to proportionately higher exposure to the risks of that sector.

• Investment style risk, which is the chance that returns from large-capitalization stocks will trail returns from the overall stock market. Large-cap stocks tend to go through cycles of doing better-or worse-than other segments of the stock market or the stock market in general. These periods have, in the past, lasted for as long as several years.

• Index replicating risk, which is the chance that the Portfolio may be prevented from holding one or more securities in the same proportion as in its target index.

An investment in the Portfolio 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 Portfolio. The bar chart shows how the performance of the Portfolio has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the Portfolio compare with those of its target index and another comparative index, which have investment characteristics similar to those of the Portfolio. The Portfolio's returns

are net of its expenses, but do not reflect additional fees and expenses that are deducted by the annuity or life insurance program through which you invest. If such fees and expenses were included in the calculation of the Portfolio's returns, the returns would be lower. Keep in mind that the Portfolio's past performance does not indicate how the Portfolio will perform in the future.Updated performance information is available on our website for Financial Advisors at advisors.vanguard.com or by calling Vanguard toll-free at 800-522-5555.

Annual Total Returns - Equity Index Portfolio

During the periods shown in the bar chart, the highest and lowest returns for a calendar quarter were:

	Total Return	Quarter
Highest	20.53 %	June 30, 2020
Lowest	-19.66 %	March 31, 2020

Average Annual Total Returns for Periods Ended December 31, 2023

	1 Year	5 Years	10 Years
Equity Index Portfolio	26.11 %	15.52 %	11.88 %
Standard & Poor's 500 Index (reflects no deduction for fees, expenses, or taxes)	26.29 %	15.69 %	12.03 %
Dow Jones U.S. Total Stock Market Float Adjusted Index (reflects no deduction for fees, expenses, or taxes)	26.06	15.05	11.40

Investment Advisor

The Vanguard Group, Inc. (Vanguard)

Portfolio Managers

Aurélie Denis, CFA, Portfolio Manager at Vanguard. She has co-managed the Fund since February 2023.

Michelle Louie, CFA, Portfolio Manager and Principal of Vanguard. She has co-managed the Portfolio since 2017.

Tax Information

The Portfolio normally distributes its net investment income and net realized capital gains, if any, to its shareholders, which are the insurance company separate accounts that sponsor your variable annuity or variable life insurance contract. The tax consequences to you of your investment in the Portfolio depend on the provisions of the annuity or life insurance contract through which you invest. For more information on taxes, please refer to the prospectus of the annuity or life insurance contract through which Portfolio shares are offered.

Payments to Financial Intermediaries

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

CFA® is a registered trademark owned by CFA Institute.

The S&P 500 Index is a product of S&P Dow Jones Indices LLC, a division of S&P Global, or its affiliates ("SPDJI") and has been licensed for use by Vanguard. Standard & Poor's® and S&P®are registered trademarks of Standard & Poor's Financial Services LLC, a division of S&P Global ("S&P") and Dow Jones® is a registered trademark of Dow Jones Trademark Holdings LLC ("Dow Jones"). The trademarks have been licensed to SPDJI and have been sublicensed for use for certain purposes by Vanguard. Vanguard Variable Insurance Funds Equity Index Portfolio is not sponsored, endorsed, sold or promoted by SPDJI, Dow Jones, S&P, or any of their respective affiliates (collectively, "S&P Dow Jones Indices"). S&P Dow Jones Indices makes no representation or warranty, express or implied, to the owners of Vanguard Variable Insurance Funds Equity Index Portfolio or any member of the public regarding the advisability of investing in securities generally or in Vanguard Variable Insurance Funds Equity Index Portfolio particularly or the ability of the S&P 500 Index to track general market performance. S&P Dow Jones Indices' only relationship to Vanguard with respect to the S&P 500 Index is the licensing of the Index and certain trademarks, service marks and/or trade names of S&P Dow Jones Indices and/or its licensors. The S&P 500 Index is determined, composed and calculated by S&P Dow Jones Indices without regard to Vanguard or Vanguard Variable Insurance Funds Equity Index Portfolio. S&P Dow Jones Indices has no obligation to take the needs of Vanguard or the owners of Vanguard Variable Insurance Funds Equity Index Portfolio into consideration in determining, composing or calculating the S&P 500 Index. S&P Dow Jones Indices is not responsible for and has not participated in the determination of the prices, and amount of Vanguard Variable Insurance Funds Equity Index Portfolio or the timing of the issuance or sale of Vanguard Variable Insurance Funds Equity Index Portfolio or in the determination or calculation of the equation by which Vanguard Variable Insurance Funds Equity Index Portfolio is to be converted into cash, surrendered or redeemed, as the case may be. S&P Dow Jones Indices has no obligation or liability in connection with the administration, marketing or trading of Vanguard Variable Insurance Funds Equity Index Portfolio. There is no assurance that investment products based on the S&P 500 Index will accurately track index performance or provide positive investment returns. S&P Dow Jones Indices LLC is not an investment advisor. Inclusion of a security within an index is not a recommendation by S&P Dow Jones Indices to buy, sell, or hold such security, nor is it considered to be investment advice.

S&P DOW JONES INDICES DOES NOT GUARANTEE THE ADEQUACY, ACCURACY, TIMELINESS AND/OR THE COMPLETENESS OF THE S&P 500 INDEX OR ANY DATA RELATED THERETO OR ANY COMMUNICATION, INCLUDING BUT NOT LIMITED TO, ORAL OR WRITTEN COMMUNICATION (INCLUDING ELECTRONIC COMMUNICATIONS) WITH