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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-01-26</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001825724</issuerCik>
        <issuerName>Population Health Investment Co., Inc.</issuerName>
        <issuerTradingSymbol>PHIC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001198321</rptOwnerCik>
            <rptOwnerName>CHAMPSI FARAH</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O POPULATION HEALTH INVESTMENT CO.,INC</rptOwnerStreet1>
            <rptOwnerStreet2>ONE WORLD FINANCIAL CENTER</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10281</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Class B Ordinary Shares</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2021-01-26</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>43125</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>250.00</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Class A Ordinary Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>43125</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>43125</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">As described in the issuer's registration statement on Form S-1 (File No. 333-249756) under the heading &quot;Description of Securities--Founder Shares&quot;, the Class B ordinary shares, par value $0.0001 per share, will automatically convert into Class A ordinary shares, par value $0.0001 per share, of the issuer at the time of the issuer's initial business combination, or earlier at the option of the holder, on a one-for-one basis, subject to adjustment for share splits, share capitalizations, reorganizations, recapitalizations and the like, and certain anti-dilution rights and have no expiration date.</footnote>
        <footnote id="F2">In connection with Ms. Champsi's election as an independent director of the issuer, 43,125 Class B ordinary shares of the issuer were transferred by Population Health Investment Holding, Inc. to Ms. Champsi for $250.00, or approximately $0.0058 per share.</footnote>
    </footnotes>

    <remarks>The Power of Attorney given by Ms. Champsi was previously filed with the U.S. Securities &amp; Exchange Commission on November 17, 2020 as an exhibit to a statement on Form 3 filed by Ms. Champsi with respect to Population Health Investment Co., Inc. and is hereby incorporated by reference.</remarks>

    <ownerSignature>
        <signatureName>/s/ Christopher Visioli, Attorney-in-Fact</signatureName>
        <signatureDate>2021-01-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
