Summary Prospectus dated February 1, 2024

as revised October 3, 2024

Calvert International Responsible Index Fund

Class / Ticker A / CDHAX I / CDHIX R6 / CDHRX

This Summary Prospectus is designed to provide investors with key fund information in a clear and concise format. Before you invest, you may want to review the Fund's Prospectus and Statement of Additional Information, which contain more information about the Fund and its risks. The Fund's Prospectus and Statement of Additional Information both dated February 1, 2024, as may be amended or supplemented, are incorporated by reference into this Summary Prospectus. For free paper or electronic copies of the Fund's Prospectus, Statement of Additional Information, annual and semi-annual shareholder reports, and other information about the Fund, go to http://www.calvert.com/prospectus, email a request to [email protected], call 1-800-368-2745, or ask any financial advisor, bank, or broker-dealer who offers shares of the Fund. Unless otherwise noted, page number references refer to the current Prospectus for this Fund.

Investment Objective

The Fund's investment objective is to seek to track the performance of the Calvert International Responsible Index (the "Index"), which measures the investment return of stocks issued by companies that are located in countries (other than the U.S.) with developed markets.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Investors may also pay commissions or other fees to their financial intermediary, which are not reflected below. You may qualify for a reduced sales charge on purchases of Class A shares if you invest, or agree to invest over a 13-month period, at least $50,000 in Calvert funds. Certain financial intermediaries also may offer variations in Fund sales charges to their customers as described in Appendix B - Financial Intermediary Sales Charge Variations in the Fund's Prospectus. More information about these and other discounts is available from your financial intermediary and under "Sales Charges" on page 38 of the Fund's Prospectus and page 20 of the Fund's Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)	Class A	Class I	Class R6
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price)	4.75%	None	None
Maximum Deferred Sales Charge (load) (as a percentage of the lower of net asset value at purchase or redemption)	None(1)	None	None

(1)	Class A shares purchased at net asset value in amounts of $1 million or more are subject to a 0.25% contingent deferred sales charge if redeemed within 12 months of purchase.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)	Class A	Class I	Class R6
Management Fees	0.24%	0.24%	0.24%
Distribution and Service (12b-1) Fees	0.25%	None	None
Other Expenses	0.16%	0.16%	0.13%
Total Annual Fund Operating Expenses	0.65%	0.40%	0.37%
Less Fee Waiver and/or Expense Reimbursement(1)	(0.11)%	(0.11)%	(0.11)%
Total Annual Fund Operating Expenses after Fee Waiver and/or Expense Reimbursement	0.54%	0.29%	0.26%

(1)

Calvert Research and Management ("CRM") has agreed to reimburse the Fund's expenses to the extent that Total Annual Fund Operating Expenses exceed 0.54% for Class A shares, 0.29% for Class I shares and 0.26% for Class R6 shares. This expense reimbursement will continue through February 1, 2025. Any amendment to or termination of this reimbursement would require approval of the Board of Directors. The expense reimbursement relates to ordinary operating expenses only and does not include expenses such as: brokerage commissions, acquired fund fees and expenses of unaffiliated funds, borrowing costs (including borrowing costs of any acquired funds), taxes or litigation expenses. Amounts reimbursed may be recouped by CRM during the same fiscal year to the extent actual expenses are less than any contractual expense cap in place during such year. Pursuant to this arrangement CRM may recoup from the Fund any reimbursed expenses during the same fiscal year if such recoupment does not cause the Fund's Total Annual Operating Expenses after such recoupment to exceed (i) the expense limit in effect at the time of reimbursement; or (ii) the expense limit in effect at the time of recoupment.

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 redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, that the operating expenses remain the same and that any expense reimbursement arrangement remains in place for the contractual 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
Class A shares	$528	$663	$810	$1,237
Class I shares	$30	$117	$213	$494
Class R6 shares	$27	$108	$197	$457

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" the portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 20% of the average value of its portfolio.

Principal Investment Strategies

The Fund employs a passive management strategy designed to track, as closely as possible, the performance of the Index. The Fund invests in the common stock of each company in the Index in approximately the same proportion as represented in the Index itself. The Fund will normally invest at least 95% of its net assets, including borrowings for investment purposes, in securities contained in the Index (the "95% Policy"). The Fund may also lend its securities.

Calvert International Responsible Index. The Index is composed of common stocks of large companies in developed markets, excluding the U.S. Large companies in developed markets are selected from the 1,000 large publicly traded companies, excluding business development companies, in markets that CRM determines to be developed markets based on a set of criteria including level of economic development, existence of capital controls, openness to foreign direct investment, market trading and liquidity conditions, regulatory environment, treatment of minority shareholders, and investor expectations. When determining 1,000 large publicly traded companies, CRM generally includes the 500 largest publicly traded companies located in or tied economically to Europe and the 500 largest publicly traded companies located in or tied economically to other non-U.S. and non-European developed markets. The Calvert Principles for Responsible Investment (the "Calvert Principles") serve as a framework for considering environmental, social and governance ("ESG") factors. Stocks are weighted in the Index based on their float-adjusted market capitalization, by country and by sector, subject to certain prescribed limits. The Index is owned by CRM, which also serves as investment adviser to the Fund. Christopher Madden, CFA, Co-Head of Applied Responsible Investment Solutions, and Zi Ye, Index Manager, manage the Index construction process at CRM.

As of December 31, 2023, the Index included 815 companies, and the market capitalization ranged from approximately $2.3 billion to $501.1 billion with a weighted average market capitalization of approximately $96.8 billion. Market capitalizations of companies within the Index are subject to change. The number of companies in the Index will change over time due to CRM's evaluation of an issuer relative to the Calvert Principles or corporate actions involving companies in the Index. The Index is reconstituted annually and is rebalanced quarterly.

Indexing. An index is a group of securities whose overall performance is used as a standard to measure investment. An index (or "passively managed") fund tries to match, as closely as possible, the performance of an established target index. An index fund's goal is to mirror the target index whether the index is going up or down. To track the Index as closely as possible, the Fund attempts to remain fully invested in stocks. The Fund may enter into foreign currency transactions, including foreign forward currency exchange contracts, in the course of purchasing and selling foreign currency denominated securities in order to track, as closely as possible, the performance of the Index.

The Fund uses a replication method of indexing. The replication method involves holding every security in the Index in approximately the same proportion as the Index. Unlike the Index, however, the Fund is subject to certain regulatory requirements that can limit its ability to fully replicate the Index. For example, the Fund is subject to diversification and concentration limitations that can require the Fund's holdings to materially deviate from the Index.

If Fund assets should ever decline to below $5 million, the Fund may use the sampling method. The sampling method involves selecting a representative number of securities that will resemble the Index in terms of key risk and other characteristics.

Principal Risks

Market Risk. The value of investments held by the Fund may increase or decrease in response to social, economic, political, financial, public health crises or other disruptive events (whether real, expected or perceived) in the U.S. and global markets and include events such as war, natural disasters, epidemics and pandemics, terrorism, conflicts and social unrest. These events may negatively impact broad segments of businesses and populations and may exacerbate pre-existing risks to the Fund. The frequency and magnitude of resulting changes in the value of the Fund's investments cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in reaction to changing market conditions. Monetary and/or fiscal actions taken by U.S. or foreign governments to stimulate or stabilize the global economy may not be effective and could lead to high market volatility.

Tracking Error Risk. Tracking error risk refers to the risk that the Fund's performance may not match or correlate to that of the Index it attempts to track, either on a daily or aggregate basis. Factors such as Fund expenses, imperfect correlation between the Fund's investments and the Index, rounding of share prices, changes to the composition of the Index, regulatory policies, limitations on Fund investments imposed by Fund diversification and/or concentration policies, high portfolio turnover rate and the use of leverage all contribute to tracking error. Tracking error risk may cause the Fund's performance to be less than expected.

Passive Investment Risk. The Fund is managed using a passive investment strategy and expects to hold common stocks of each company in the Index regardless of their current or projected performance. The Fund generally will not adjust its portfolio investments to attempt to take advantage of market opportunities or lessen the impact of a market decline or a decline in the performance of one or more issuers. Maintaining investments regardless of market conditions or the performance of individual investments could cause the Fund's return to be lower than if the Fund employed an active strategy. Unusual market events may increase market volatility and may cause the characteristics of the Index components to vary from those expected under normal circumstances.

Equity Securities Risk. The value of equity securities and related instruments may decline in response to adverse changes in the economy or the economic outlook; deterioration in investor sentiment; interest rate, currency, and commodity price fluctuations; adverse geopolitical, social or environmental developments; issuer and sector-specific considerations; unexpected trading activity among retail investors; or other factors. Market conditions may affect certain types of stocks to a greater extent than other types of stocks. If the stock market declines in value, the value of the Fund's equity securities will also likely decline. Although prices can rebound, there is no assurance that values will return to previous levels.

Real Estate Risk. Real estate investments are subject to risks associated with owning real estate, including declines in real estate values, increases in property taxes, fluctuations in interest rates, limited availability of mortgage financing, decreases in revenues from underlying real estate assets, declines in occupancy rates, changes in government regulations affecting zoning, land use, and rents, environmental liabilities, and risks related to the management skill and creditworthiness of the issuer. Companies in the real estate industry may also be subject to liabilities under environmental and hazardous waste laws, among others. REITs must satisfy specific requirements for favorable tax treatment and can involve unique risks in addition to the risks generally affecting the real estate industry. Changes in underlying real estate values may have an exaggerated effect to the extent that investments are concentrated in particular geographic regions or property types.

Foreign Investment Risk. Foreign investments can be adversely affected by political, economic and market developments abroad, including the imposition of economic and other sanctions by the United States or another country against a particular country or countries, organizations, entities and/or individuals. There may be less publicly available information about foreign issuers because they may not be subject to reporting practices, requirements or regulations comparable to those to which United States companies are subject. Adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. Foreign markets may be smaller, less liquid and more volatile than the major markets in the United States and, as a result, Fund share values may be more volatile. Trading in foreign markets typically involves higher expense than trading in the United States. The Fund may have difficulties enforcing its legal or contractual rights in a foreign country. Depositary receipts are subject to many of the risks associated with investing directly in foreign instruments, including the political and economic risks of the underlying issuer's country and, in the case of depositary receipts traded on foreign markets, currency risk.

Currency Risk. Exchange rates for currencies fluctuate daily. The value of foreign investments may be affected favorably or unfavorably by changes in currency exchange rates in relation to the U.S. dollar. Currency markets generally are not as regulated as securities markets and currency transactions are subject to settlement, custodial and other operational risks.

Derivatives Risk. The Fund's exposure to derivatives involves risks different from, or possibly greater than, the risks associated with investing directly in securities and other investments. The use of derivatives can lead to losses because of adverse movements in the price or value of the security, instrument, index, currency, commodity, economic indicator or event underlying a derivative ("reference instrument"), due to failure of a counterparty or due to tax or regulatory constraints. Derivatives may create leverage in the Fund, which represents a non-cash exposure to the underlying reference instrument. Leverage can increase both the risk and return potential of the Fund. Derivatives risk may be more significant when derivatives are used to enhance return or as a substitute for a cash investment position, rather than solely to hedge the risk of a position held by the Fund. Use of derivatives involves the exercise of specialized skill and judgment, and a transaction may be unsuccessful in whole or in part because of market behavior or unexpected events. Changes in the value of a derivative (including one used for hedging) may not correlate perfectly with the underlying reference instrument. Derivative instruments traded in over-the-counter markets may be difficult to value, may be illiquid, and may be subject to wide swings in valuation caused by changes in the value of the underlying reference instrument. If a derivative's counterparty is unable to honor its commitments, the value of Fund shares may decline and the Fund could experience delays in (or be unable to achieve) the return of collateral or other assets held by the counterparty. The loss on derivative transactions may substantially exceed the initial investment. A derivative investment also involves the risks relating to the reference instrument underlying the investment.

Securities Lending Risk. Securities lending involves a possible delay in recovery of the loaned securities or a possible loss of rights in the collateral if the borrower fails financially. The Fund could also lose money if the value of the collateral decreases.

Liquidity Risk. The Fund is exposed to liquidity risk when trading volume, lack of a market maker or trading partner, large position size, market conditions, or legal restrictions impair its ability to sell particular investments or to sell them at advantageous market prices. Consequently, the Fund may have to accept a lower price to sell an investment or continue to hold it or keep the position open, sell other investments to raise cash or abandon an investment opportunity, any of which could have a negative effect on the Fund's performance. These effects may be exacerbated during times of financial or political stress.

Responsible Investing Risk. Investing primarily in responsible investments carries the risk that, under certain market conditions, the Fund's performance may be impacted. The application of responsible investment criteria may affect the Fund's exposure to certain sectors or types of investments, and may impact the Fund's relative investment performance depending on whether such sectors or investments are in or out of favor in the market. An investment's ESG performance or the investment adviser's assessment of such performance may change over time, which could cause the Fund to temporarily hold securities that do not comply with the Fund's responsible investment criteria. In evaluating an investment, the investment adviser is dependent upon information and data that may be incomplete, inaccurate or unavailable, which could adversely affect the analysis of the ESG factors relevant to a particular investment. Successful application of the Fund's responsible investment strategy will depend on the investment adviser's skill in properly identifying and analyzing material ESG issues.

General Fund Investing Risks. The Fund is not a complete investment program and there is no guarantee that the Fund will achieve its investment objective. It is possible to lose money by investing in the Fund. The Fund is designed to be a long-term investment vehicle and is not suited for short-term trading. Investors in the Fund should have a long-term investment perspective and be able to tolerate potentially sharp declines in value. Purchase and redemption activities by Fund shareholders may impact the management of the Fund and its ability to achieve its investment objective(s). In addition, the redemption by one or more large shareholders or groups of shareholders of their holdings in the Fund could have an adverse impact on the remaining shareholders in the Fund. The Fund relies on various service providers, including the investment adviser and sub-adviser, if applicable, in its operations and is susceptible to operational, information security and related events (such as public health crises, cyber or hacking attacks) that may affect the service providers or the services that they provide to the Fund. An investment in the Fund is not a deposit in a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Performance

The following bar chart and table provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and how the Fund's average annual returns over time compare with those of the Index and a broad-based securities market index. The returns in the bar chart are for Class A shares and do not reflect a sales charge. If the sales charge was reflected, the returns would be lower. Past performance (both before and after taxes) is not necessarily an indication of how the Fund will perform in the future.

CRM became the investment adviser to the Fund on December 31, 2016. Performance reflected prior to such date is that of the Fund's former investment adviser. The Fund's performance reflects the effects of expense reductions. Absent these reductions, performance would have been lower. Updated Fund performance information can be obtained by visiting www.calvert.com.

For the period from December 31, 2015 through December 31, 2023, the highest quarterly total return for Class A was 17.67% for the quarter ended June 30, 2020 and the lowest quarterly return was -21.21% for the quarter ended March 31, 2020.

Average Annual Total Returns as of December 31, 2023	One Year	Five Years	Life of Fund
Class A Return Before Taxes	13.98%	8.04%	5.50%
Class A Return After Taxes on Distributions	13.71%	7.84%	5.23%
Class A Return After Taxes on Distributions and Sale of Class A Shares	8.83%	6.51%	4.45%
Class I Return Before Taxes	19.99%	9.37%	6.44%
Class R6 Return Before Taxes	20.00%	9.39%	6.45%
MSCI World ex USA Index (reflects net dividends, which reflects the deduction of withholding taxes)	17.94%	8.45%	5.83%
Calvert International Responsible Index (reflects net dividends, which reflects the deduction of withholding taxes)	20.34%	9.58%	6.48%

These returns reflect the maximum sales charge for Class A (4.75%). Class A and Class I commenced operations on October 30, 2015. The Class R6 performance shown above for the period prior to February 1, 2019 (commencement of operations) is the performance of Class I shares at net asset value without adjustment for any differences in the expenses of the two classes. If adjusted for such differences, returns would be different.

Source for the MSCI World ex USA Index: MSCI. MSCI data may not be reproduced or used for any other purpose. MSCI provides no warranties, has not prepared or approved this report, and has no liability hereunder. Investors cannot invest directly in an Index.

After-tax returns are calculated using the highest historical individual federal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on a shareholder's tax situation and the actual characterization of distributions, and may differ from those shown. After-tax returns are not relevant to shareholders who hold shares in tax-deferred accounts or to shares held by non-taxable entities. After-tax returns for other Classes of shares will vary from the after-tax returns presented for Class A shares. Return After Taxes on Distributions for a period may be the same as Return Before Taxes for that period because no taxable distributions were made during that period. Also, Return After Taxes on Distributions and Sale of Fund Shares for a period may be greater than or equal to Return Before Taxes and/or Return After Taxes on Distributions for the same period because of losses realized on the sale of Fund shares.

Management

Investment Adviser. Calvert Research and Management ("CRM" or the "Adviser").

Portfolio Managers

Jennifer Mihara, Managing Director of Morgan Stanley and Vice President of CRM, has managed the Fund since July 1, 2024.

Thomas C. Seto, Managing Director of Morgan Stanley and Vice President of CRM, has managed the Fund since December 31, 2016. Mr. Seto intends to retire and will no longer serve as a Portfolio Manager of the Fund after December 31, 2024.

Gordon Wotherspoon, Managing Director of Morgan Stanley and Vice President of CRM, has managed the Fund since July 1, 2024.

Purchase and Sale of Fund Shares

You may purchase, redeem or exchange Fund shares on any business day, which is any day the New York Stock Exchange is open for business. You may purchase, redeem or exchange Fund shares either through your financial intermediary or directly from the Fund either by writing to the Fund, P.O. Box 219544, Kansas City, MO 64121-9544, or by calling 1-800-368-2745. The minimum initial purchase or exchange into the Fund is $5,000 for Class A ($2,000 for individual retirement accounts in Class A) and $1,000,000 for Class I and $5,000,000 for Class R6 (waived in certain circumstances). There is no minimum for subsequent investments.

Tax Information

If your shares are held in a taxable account, the Fund's distributions will be taxed to you as ordinary income and/or capital gains, unless you are exempt from taxation. If your shares are held in a tax-advantaged account, you will generally be taxed only upon withdrawals from the account.

Payments to Broker-Dealers and Other Financial Intermediaries

If you purchase the Fund's shares through a broker-dealer or other financial intermediary (such as a bank) (collectively, "financial intermediaries"), the Fund, its principal underwriter and its affiliates may pay the financial intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the financial intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary's website for more information.

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© 2024 Calvert Research and Management

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