Summary Prospectus by Investment Company - Form 497K

Summary Prospectus dated May 1, 2024

CVT Investment Grade Bond Index Portfolio

Class I Shares Class F Shares

This Summary Prospectus is designed to provide separate accounts of insurance companies, qualified pension and retirement plans and other eligible investors with key fund information in a clear and concise format. Before you invest, you may want to review the Portfolio's Prospectus and Statement of Additional Information, which contain more information about the Portfolio and its risks. The Portfolio's Prospectus and Statement of Additional Information, both dated May 1, 2024, as may be amended or supplemented, are incorporated by reference into this Summary Prospectus and are available at http://www.calvert.com/variable-portfolios. Contract holders, plan beneficiaries and other investors should ask their financial intermediaries, insurance companies, or plan sponsors, or visit their financial intermediary's or insurance company's web site for more information.

Investment Objective

CVT Investment Grade Bond Index Portfolio (the "Fund") seeks investment results that correspond to the total return performance of the bond market, as represented by the Bloomberg U.S. Aggregate Bond Index.

Fees and Expenses of the Fund

This table does not reflect expenses and charges that are, or may be, imposed under your variable annuity contract or variable life insurance separate account ("Variable Contract") or qualified pension or retirement plan ("Qualified Plan"). If these fees and expenses were included, expenses shown would be higher. For information on these charges, please refer to the applicable Variable Contract prospectus, prospectus summary or disclosure statement. If you participate through a Qualified Plan, the table does not reflect direct expenses of the plan, and you should consult your administrator for more information.

This table describes the expenses that you may pay if you buy and hold shares of the Fund.

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

Annual Fund Operating Expenses (expenses you pay each year as a percentage of the value of your investment)	Class I	Class F
Management Fees	0.32%	0.32%
Distribution and Service (12b-1) Fees	None	0.25%
Other Expenses	0.17%	0.17%
Total Annual Fund Operating Expenses	0.49%	0.74%
Expense Reimbursement(1)	(0.17)%	(0.17)%
Total Annual Fund Operating Expenses After Expense Reimbursement	0.32%	0.57%

(1)

Calvert Research and Management ("CRM") has agreed to reimburse the Fund's expenses to the extent that Total Annual Fund Operating Expenses exceed 0.32% for Class I shares and 0.57% for Class F shares. This expense reimbursement will continue through May 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 Fund Operating Expenses after such recoupment to exceed (i) the expense limit in effect at the time of the 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 does not reflect expenses and charges which are, or may be, imposed under your Variable Contract or Qualified Plan. If these fees and expenses were included, expenses shown would be higher. 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 I shares	$33	$140	$257	$600
Class F shares	$58	$219	$395	$902

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. 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 11% of the average value of its portfolio.

Principal Investment Strategies

The Fund seeks to track the total return of the securities composing the Bloomberg U.S. Aggregate Bond Index (the "Index"), taking into consideration redemptions, sales of additional shares, and other adjustments described below. Under normal circumstances, the Fund will invest at least 80% of its net assets (plus any borrowings for investment purposes) in investments with economic characteristics similar to the fixed-income securities represented in the Index. The Index is an unmanaged index of 13,334 U.S. Treasury, government-related and investment grade corporate and securitized fixed-income securities with a total market value of $26.7 trillion as of December 31, 2023. The Index is primarily composed of:

·	Obligations issued or guaranteed by the U.S. Government or its agencies or instrumentalities; and

·

Corporate securities, mortgage-backed pass-through securities ("MBS"), asset-backed securities ("ABS") and commercial mortgage-backed securities (agency and non-agency) ("CMBS") publicly offered for sale in the United States. Securities eligible for inclusion in the Index may be registered with the U.S. Securities and Exchange Commission or exempt from registration at the time of issuance and Rule 144A securities with registration rights.

Securities included in the Index must be rated investment grade (BBB- or higher from S&P Global Ratings ("S&P") or by Fitch Ratings, or Baa3 or higher from Moody's Investors Service, Inc. ("Moody's")). Unrated securities may be included in the Index if an issuer rating is available or if there is an expected rating at issuance.

As of December 31, 2023, the weighted average maturity of the securities in the Index was 8.46 years, the weighted average coupon was 3.09% and the weighted average modified duration was 6.24 years. The Index includes all "index-eligible" securities that meet minimum par amounts outstanding. The Index is rebalanced monthly. Although the Fund is not rebalanced monthly like the Index, adjustments are made to accommodate high-level changes with respect to the composition and characteristics of the Index. The Fund is not sponsored, endorsed, sold or promoted by Bloomberg LP.

The Fund will invest primarily in fixed-income securities that compose the Index. While not required, the Fund will generally sell securities that the Index provider removes from the Index. The Fund may also invest in exchange-traded funds ("ETFs") that provide exposure to the Index. Derivatives such as options and futures, and options on such futures that provide exposure to securities in the Index may be held by the Fund incidental to its main investment strategy in order to manage cash balances, to maintain liquidity to meet shareholder redemptions, or minimize trading costs. The Fund may also lend its securities.

The Fund uses a representative sampling method in seeking to track the total return of the securities in the Index. The Fund generally purchases securities that are components of the Index, except that the Fund will not purchase bonds that are rated below investment grade at the time of purchase. If a bond held in the Fund is downgraded to a rating below investment grade (so-called "junk bonds"), the Fund may continue to hold the security until such time as the Sub-Adviser deems it most advantageous to dispose of the security. The Fund intends to concentrate its investments only to the extent that the Index does.

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. No active trading market may exist for certain investments held by the Fund, which may impair the ability of the Fund to sell or to realize the current valuation of such investments in the event of the need to liquidate such assets.

Passive Investment Risk. The Fund is managed using a passive investment strategy and expects to hold components of 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.

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, 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.

Sector Risk. The Fund may invest a significant portion of its assets in one or more sectors, if the Index does so. As such, the value of Fund shares may be affected by events that adversely affect such sector(s), and may fluctuate more than that of a fund that invests more broadly.

Credit Risk. Investments in fixed-income and other debt obligations (referred to below as "debt instruments") are subject to the risk of non-payment of scheduled principal and interest. Changes in economic conditions or other circumstances may reduce the capacity of the party obligated to make principal and interest payments on such instruments and may lead to defaults. Such non-payments and defaults may reduce the value of Fund shares and income distributions. The value of debt instruments also may decline because of concerns about the issuer's ability to make principal and interest payments. In addition, the credit ratings of debt instruments may be lowered if the financial condition of the party obligated to make payments with respect to such instruments deteriorates. In the event of bankruptcy of the issuer of a debt instrument, the Fund could experience delays or limitations with respect to its ability to realize the benefits of any collateral securing the instrument. In order to enforce its rights in the event of a default, bankruptcy or similar situation, the Fund may be required to retain legal or similar counsel, which may increase the Fund's operating expenses and adversely affect net asset value.

Interest Rate Risk. In general, the value of income securities will fluctuate based on changes in interest rates. The value of these securities is likely to increase when interest rates fall and decline when interest rates rise. Duration measures the time-weighted expected cash flows of a fixed-income security, while maturity refers to the amount of time until a fixed-income security matures. Generally, securities with longer durations or maturities are more sensitive to changes in interest rates than securities with shorter durations or maturities, causing them to be more volatile. Conversely, fixed-income securities with shorter durations or maturities will be less volatile but may provide lower returns than fixed-income securities with longer durations or maturities. In a rising interest rate environment, the duration of income securities that have the ability to be prepaid or called by the issuer may be extended. In a declining interest rate environment, the proceeds from prepaid or maturing instruments may have to be reinvested at a lower interest rate. Certain instruments held by the Fund were historically based on the London Interbank Offered Rate ("LIBOR"), which was the average offered rate for various maturities of short-term loans between certain major international banks. LIBOR historically was used throughout global banking and financial industries to determine interest rates for a variety of financial instruments (such as debt instruments and derivatives) and borrowing arrangements. Upon a determination by regulators to phase out the use of LIBOR, market participants have been transitioning to the use of alternative reference rates over the past few years. As of June 30, 2023, the administrator of LIBOR ceased publishing LIBOR settings. The impact of the transition away from LIBOR on certain debt securities, derivatives and other financial instruments that utilize LIBOR remains uncertain. The transition away from LIBOR and the use of replacement rates may adversely affect transactions that used LIBOR as a reference rate, financial institutions, funds and other market participants that engaged in such transactions, and the financial markets generally.

Mortgage- and Asset-Backed Securities Risk.Mortgage- and asset-backed securities represent interests in "pools" of commercial or residential mortgages or other assets, including consumer loans or receivables. Movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain types of mortgage- and asset-backed securities. Although certain mortgage- and asset-backed securities are guaranteed as to timely payment of interest and principal by a government entity, the market price for such securities is not guaranteed and will fluctuate. The purchase of mortgage- and asset-backed securities issued by non-government entities may entail greater risk than such securities that are issued or guaranteed by a government entity. Mortgage- and asset-backed securities issued by non-government entities may offer higher yields than those issued by government entities, but may also be subject to greater volatility than government issues and can also be subject to greater credit risk and the risk of default on the underlying mortgages or other assets. Investments in mortgage- and asset-backed securities are subject to both extension risk, where borrowers pay off their debt obligations more slowly in times of rising interest rates, and prepayment risk, where borrowers pay off their debt obligations sooner than expected in times of declining interest rates.

U.S. Government Securities Risk. Different types of U.S. government securities are subject to different levels of credit risk, including the risk of default, depending on the nature of the particular government support for that security. Although certain U.S. Government-sponsored agencies (such as the Federal Home Loan Mortgage Corporation and the Federal National Mortgage Association) may be chartered or sponsored by acts of Congress, their securities are neither issued nor guaranteed by the U.S. Treasury. With respect to U.S. government securities that are not backed by the full faith and credit of the United States, there is a risk that the U.S. Government will not provide financial support to such U.S. government agencies, instrumentalities or sponsored enterprises if not obligated to do so by law. U.S. Treasury and U.S. Government agency securities generally have a lower return than other obligations because of their higher credit quality and market liquidity.

ETF Risk. ETFs are subject to the risks of investing in the underlying securities or other investments. ETF shares may trade at a premium or discount to net asset value and are subject to secondary market trading risks. In addition, the Fund will bear a pro rata portion of the operating expenses of an ETF in which it invests.

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.

Restricted Securities Risk. Unless registered for sale to the public under applicable federal securities law, restricted securities can be sold only in private transactions to qualified purchasers pursuant to an exemption from registration. The sale price realized from a private transaction could be less than the Fund's purchase price for the restricted security. It may be difficult to identify a qualified purchaser for a restricted security held by the Fund and such security could be deemed illiquid. It may also be more difficult to value such securities.

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.

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.

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 one or more indexes intended to measure broad market performance. The Fund's primary benchmark index was changed from the Bloomberg U.S. Aggregate Bond Index to the Bloomberg U.S. Universal Index effective May 1, 2024 to comply with the regulation that requires the Fund's primary benchmark to represent the overall applicable market. The additional index(es) in the table provide a means to compare the Fund's average annual returns to a benchmark that CRM believes is representative of the Fund's investment universe. The returns in the bar chart are for Class I shares and do not reflect any insurance-related expenses and charges under a Variable Contract or expenses related to a Qualified Plan. If such charges were reflected, the returns would be lower. Thus, you should not compare the Fund's returns directly with the performance of other products without taking into account all insurance-related charges and expenses payable under your Variable Contract or Qualified Plan. Past performance 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.

For the ten years ended December 31, 2023, the highest quarterly total return for Class I was 6.58% for the quarter ended December 31, 2023 and the lowest quarterly return was -5.63% for the quarter ended March 31, 2022.

Average Annual Total Return as of December 31, 2023	One Year	Five Years	Ten Years
Class I Return Before Taxes	5.47%	1.06%	1.68%
Class F Return Before Taxes	5.22%	0.81%	1.48%
Bloomberg U.S. Universal Index (reflects no deduction for fees, expenses or taxes)	6.17%	1.44%	2.08%
Bloomberg U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)	5.53%	1.10%	1.81%

The Class F performance shown above for the period prior to October 30, 2015 (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.

BLOOMBERG^® is a trademark and service mark of Bloomberg Finance L.P. and its affiliates (collectively "Bloomberg"). BARCLAYS^® is a trademark and service mark of Barclays Bank Plc (collectively with its affiliates, "Barclays"), used under license. Bloomberg or Bloomberg's licensors, including Barclays, own all proprietary rights in the Bloomberg Barclays Indices. Neither Bloomberg nor Barclays is affiliated with CRM, and neither approves, endorses, reviews or recommends the Fund. Neither Bloomberg nor Barclays guarantees the timeliness, accurateness or completeness of any data or information relating to Bloomberg U.S. Universal Index and Bloomberg U.S. Aggregate Bond Index, and neither shall be liable in any way to CRM, investors in the Fund or other third parties in respect of the use or accuracy of Bloomberg U.S. Universal Index and Bloomberg U.S. Aggregate Bond Index or any data included therein. Investors cannot invest directly in an Index.

Management

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

Investment Sub-Adviser. Ameritas Investment Partners, Inc. ("AIP").

Portfolio Manager. K. Jessie Goodwin, CFA, Vice President and Managing Director of AIP, has managed the Fund since May 2023 and has assisted in trading and strategy since 2014.

Purchase and Sale of Fund Shares

All purchases, redemptions and exchanges of Fund shares are made through insurance company separate accounts, qualified pension and retirement plans or by other eligible investors that are the record owner of the shares. Contract holders, plan beneficiaries, and other investors seeking to purchase, redeem, or exchange interest in the Fund's shares should consult with the insurance company, plan sponsor or other eligible investor through which their investment in the Fund is made.

Tax Information

The Fund will distribute any net investment income and net realized capital gains at least annually. Both types of distributions will be made in shares of the Fund unless an election is made on behalf of a separate account to receive some or all of the distributions in cash. Because shares of the Fund are offered to insurance company separate accounts, qualified pension and retirement plans, and other eligible investors, you should read your prospectus, disclosure statement or plan documentation to understand the tax treatment of your investment.

Payments to Insurance Companies, Plan Sponsors and Other Financial Intermediaries

The Fund is generally available for purchase by separate accounts of insurance companies, qualified pension and retirement plans or by other eligible investors. The Fund, its principal underwriter and its affiliates may make payments to insurance companies, plan sponsors or other financial intermediaries for distribution and related services. These payments may create a conflict of interest for the insurance company, plan sponsor or other financial intermediary to include the Fund as an investment option in their product or to recommend the Fund over another investment option. Ask your financial intermediary, insurance company, or plan sponsor, or visit your financial intermediary's or insurance company's website, for more information.

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© 2024 Calvert Research and Management

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