<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-03-13</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001734517</issuerCik>
        <issuerName>Viela Bio, Inc.</issuerName>
        <issuerTradingSymbol>VIE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001511472</rptOwnerCik>
            <rptOwnerName>Wicki Andreas</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O VIELA BIO, INC.,</rptOwnerStreet1>
            <rptOwnerStreet2>ONE MEDIMMUNE WAY, FIRST FLOOR, AREA TWO</rptOwnerStreet2>
            <rptOwnerCity>GAITHERSBURG</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>20878</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-03-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1750000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>53.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>HBM Healthcare Investments (Cayman) Ltd.</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Reflects disposition of Issuer common stock in connection with the consummation of the transactions contemplated by the Agreement and Plan of Merger, dated January 31, 2021 (the &quot;Merger Agreement&quot;), by and among the Issuer, Horizon Therapeutics USA, Inc., Teiripic Merger Sub, Inc. (&quot;Purchaser&quot;), and for certain purposes, Horizon Therapeutics plc, including the completion on March 13, 2021 of a tender offer to purchase all of the outstanding shares of Issuer common stock at a price of $53.00 per share in cash, without interest, less any required withholding taxes (the &quot;Offer Price&quot;), and the consummation of the merger (the &quot;Merger&quot;) between the Issuer and Purchaser on on March 15, 2021. Pursuant to the Merger Agreement, as of the effective time of the Merger, each outstanding share of Issuer common stock was cancelled in exchange for the right to receive an amount equal to the Offer Price.</footnote>
        <footnote id="F2">These shares are held by HBM Healthcare Investments (Cayman) Ltd. (&quot;HBM&quot;), of which Dr. Wicki is a member of the board of directors. The board of directors of HBM acts by majority vote, and Dr. Wicki does not have sole voting or investment power with respect to the shares. Dr. Wicki disclaims beneficial ownership of such shares for the purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the &quot;Exchange Act&quot;), except to the extent of his pecuniary interest therein, if any. This report on Form 4 shall not be deemed an admission that the reporting person is a beneficial owner for the purposes of Section 16 of the Exchange Act, or for any other purpose.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/S/ MEHDI KHODADAD, ATTORNEY-IN-FACT</signatureName>
        <signatureDate>2021-03-15</signatureDate>
    </ownerSignature>
</ownershipDocument>
