SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13D

                   Under the Securities Exchange Act of 1934*

                             Nabi Biopharmaceuticals
- --------------------------------------------------------------------------------
                                (Name of Issuer)

                     Common Stock, par value $0.10 per share
- --------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                    629519109
- --------------------------------------------------------------------------------
                      (CUSIP Number of Class of Securities)

                                 Daniel S. Loeb
                                 Third Point LLC
                                 390 Park Avenue
                               New York, NY 10022
                                 (212) 224-7400
- --------------------------------------------------------------------------------
                  (Name, Address and Telephone Number of Person
                Authorized to Receive Notices and Communications)

                                   Copies to:
                            Michael A. Schwartz, Esq.
                          Willkie Farr & Gallagher LLP
                               787 Seventh Avenue
                             New York, NY 10019-6099
                                 (212) 728-8000

                                  April 5, 2006
- --------------------------------------------------------------------------------
                          (Date of Event which Requires
                            Filing of this Schedule)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
schedule because of ss.ss. 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the
following box: [ ]

NOTE: Schedules filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See Rule 240.13d-7 for other
parties to whom copies are to be sent.

* The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).




                                  SCHEDULE 13D


- --------------------------                        ------------------------------
CUSIP No. 629519109                                    Page 2 of 14 Pages
- --------------------------                        ------------------------------


- ----------- --------------------------------------------------------------------
    1       NAME OF REPORTING PERSON
            I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

            Third Point LLC                                I.D. #13-3922602
- ----------- --------------------------------------------------------------------
    2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP           (a) [ ]
                                                                       (b) [X]

- ----------- --------------------------------------------------------------------
    3       SEC USE ONLY

- ----------- --------------------------------------------------------------------
    4       SOURCE OF FUNDS*

            AF
- ----------- --------------------------------------------------------------------
    5       CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDING IS REQUIRED PURSUANT TO
            ITEMS 2(d) or 2(e) [ ]

- ----------- --------------------------------------------------------------------
    6       CITIZENSHIP OR PLACE OF ORGANIZATION

            Delaware
- --------------------- --------- ------------------------------------------------
                         7      SOLE VOTING POWER

                                0
                      --------- ------------------------------------------------
NUMBER OF                8      SHARED VOTING POWER
SHARES
BENEFICIALLY                    5,000,000
OWNED BY              --------- ------------------------------------------------
EACH                     9      SOLE DISPOSITIVE POWER
REPORTING
PERSON WITH                     0
                      --------- ------------------------------------------------
                         10     SHARED DISPOSITIVE POWER

                                5,000,000
- ----------- --------------------------------------------------------------------
    11      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH PERSON

            5,000,000
- ----------- --------------------------------------------------------------------
    12      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
            SHARES* [ ]

- ----------- --------------------------------------------------------------------
    13      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

            8.4%
- ----------- --------------------------------------------------------------------
    14      TYPE OF REPORTING PERSON*

            OO
- ----------- --------------------------------------------------------------------





                                  SCHEDULE 13D


- --------------------------                        ------------------------------
CUSIP No. 629519109                                    Page 3 of 14 Pages
- --------------------------                        ------------------------------


- ----------- --------------------------------------------------------------------
    1       NAME OF REPORTING PERSON
            I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

            Third Point Offshare Fund, Ltd.
- ----------- --------------------------------------------------------------------
    2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP           (a) [ ]
                                                                       (b) [X]

- ----------- --------------------------------------------------------------------
    3       SEC USE ONLY

- ----------- --------------------------------------------------------------------
    4       SOURCE OF FUNDS*

            AF
- ----------- --------------------------------------------------------------------
    5       CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDING IS REQUIRED PURSUANT TO
            ITEMS 2(d) or 2(e) [ ]

- ----------- --------------------------------------------------------------------
    6       CITIZENSHIP OR PLACE OF ORGANIZATION

            Cayman Islands
- --------------------- --------- ------------------------------------------------
                         7      SOLE VOTING POWER

                                0
                      --------- ------------------------------------------------
NUMBER OF                8      SHARED VOTING POWER
SHARES
BENEFICIALLY                    3,157,800
OWNED BY              --------- ------------------------------------------------
EACH                     9      SOLE DISPOSITIVE POWER
REPORTING
PERSON WITH                     0
                      --------- ------------------------------------------------
                         10     SHARED DISPOSITIVE POWER

                                3,157,800
- ----------- --------------------------------------------------------------------
    11      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH PERSON

            3,157,800
- ----------- --------------------------------------------------------------------
    12      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
            SHARES* [ ]

- ----------- --------------------------------------------------------------------
    13      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

            5.3%
- ----------- --------------------------------------------------------------------
    14      TYPE OF REPORTING PERSON*

            OO
- ----------- --------------------------------------------------------------------





                                  SCHEDULE 13D


- --------------------------                        ------------------------------
CUSIP No. 629519109                                    Page 4 of 14 Pages
- --------------------------                        ------------------------------


- ----------- --------------------------------------------------------------------
    1       NAME OF REPORTING PERSON
            I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

            Daniel S. Loeb
- ----------- --------------------------------------------------------------------
    2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP           (a) [ ]
                                                                       (b) [X]

- ----------- --------------------------------------------------------------------
    3       SEC USE ONLY

- ----------- --------------------------------------------------------------------
    4       SOURCE OF FUNDS*

            AF
- ----------- --------------------------------------------------------------------
    5       CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDING IS REQUIRED PURSUANT TO
            ITEMS 2(d) or 2(e) [ ]

- ----------- --------------------------------------------------------------------
    6       CITIZENSHIP OR PLACE OF ORGANIZATION

            United States
- --------------------- --------- ------------------------------------------------
                         7      SOLE VOTING POWER

                                0
                      --------- ------------------------------------------------
NUMBER OF                8      SHARED VOTING POWER
SHARES
BENEFICIALLY                    5,000,000
OWNED BY              --------- ------------------------------------------------
EACH                     9      SOLE DISPOSITIVE POWER
REPORTING
PERSON WITH                     0
                      --------- ------------------------------------------------
                         10     SHARED DISPOSITIVE POWER

                                5,000,000
- ----------- --------------------------------------------------------------------
    11      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH PERSON

            5,000,000
- ----------- --------------------------------------------------------------------
    12      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
            SHARES* [ ]

- ----------- --------------------------------------------------------------------
    13      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

            8.4%
- ----------- --------------------------------------------------------------------
    14      TYPE OF REPORTING PERSON*

            IN
- ----------- --------------------------------------------------------------------





     This Schedule 13D is being filed on behalf of Third Point LLC, a Delaware
limited liability company (the "Management Company"), Third Point Offshore Fund,
Ltd., a Cayman Islands limited liability exempted company (the "Offshore Fund"),
and Daniel S. Loeb, an individual ("Mr. Loeb" and, together with the Management
Company and the Offshore Fund, the "Reporting Persons"). This Schedule 13D
relates to the Common Stock, par value $0.10 per share, of Nabi
Biopharmaceuticals, a Delaware corporation (the "Company"). Unless the context
otherwise requires, references herein to the "Common Stock" are to such Common
Stock of the Company. The Management Company is the investment manager or
adviser to a variety of hedge funds and managed accounts (such funds and
accounts, collectively, including but not limited to the Offshore Fund, the
"Funds"). The Funds directly own the Common Stock to which this Schedule 13D
relates, and the Reporting Persons may be deemed to have beneficial ownership
over such Common Stock by virtue of the authority granted to them by the Funds
to vote and to dispose of the securities held by the Funds, including the Common
Stock.

Item 1.  Security and Issuer.

     This statement on Schedule 13D relates to the Common Stock of the Company
and is being filed pursuant to Rule 13d-1 under the Securities Exchange Act of
1934, as amended (the "Exchange Act"). The address of the principal executive
offices of the Company is 5800 Park of Commerce Boulevard N.W., Boca Raton,
Florida 33487.

Item 2.  Identity and Background.

     (a) This statement is filed by the Reporting Persons. Daniel S. Loeb is the
chief executive officer of the Management Company and controls the Management
Company's business activities. The Management Company is organized as a limited
liability company under the laws of the State of Delaware. The Offshore Fund is
organized as a limited liability exempted company under the laws of the Cayman
Islands.

     (b) The address of the principal business and principal office of the
Management Company and Mr. Loeb is 390 Park Avenue, 18th floor, New York, New
York 10022. The address of the principal business and principal office of the
Offshore Fund is c/o Walkers SPV Limited, Walker House, Mary Street, P.O. Box
908GT, George Town, Grand Cayman, Cayman Islands, British West Indies.

     (c) The principal business of the Management Company is to serve as
investment manager or adviser to the Funds, and to control the investing and
trading in securities of the Funds. The principal business of Mr. Loeb is to act
as the chief executive

                                       5




officer of the Management Company. The principal business of the Offshore Fund
is to invest and trade in securities.

     (d) None of the Reporting Persons, nor, to the best of their knowledge, any
of their directors, executive officers, general partners or members has, during
the last five years, been convicted in a criminal proceeding (excluding traffic
violations or similar misdemeanors).

     (e) None of the Reporting Persons, nor, to the best of their knowledge, any
of their directors, executive officers, general partners or members has, during
the last five years, been a party to a civil proceeding of a judicial or
administrative body of competent jurisdiction and as a result of such proceeding
was or is subject to a judgment, decree or final order enjoining future
violations of, or prohibiting or mandating activities subject to, federal or
state securities laws or finding any violation with respect to such laws.

     (f) Mr. Loeb is a United States citizen.

Item 3.   Source and Amount of Funds or Other Consideration.

     The Funds expended an aggregate of approximately $23,570,628 of their own
investment capital to acquire the 5,000,000 shares of Common Stock held by them
(the "Shares"), and the Offshore Fund expended an aggregate of approximately
$14,901,409 of its own investment capital to acquire its 3,157,800 shares of
Common Stock. All Shares were acquired in open market purchases on the Nasdaq
National Market.

     The Funds effect purchases of securities primarily through margin accounts
maintained for them with Bear, Stearns Securities Corp. and Goldman, Sachs &
Co., which may extend margin credit to the Funds as and when required to open or
carry positions in the margin accounts, subject to applicable Federal margin
regulations, stock exchange rules and the firm's credit policies. In such
instances, the positions held in the margin accounts are pledged as collateral
security for the repayment of debit balances in the accounts.

Item 4. Purpose of Transaction.

     The purpose of the acquisition of the Shares by the Funds is for
investment. The Reporting Persons may cause the Funds to make further
acquisitions of Common Stock from time to time or to dispose of any or all of
the shares of Common Stock held by the Funds at any time.

     The Reporting Persons believe that the market price of the Common Stock
materially understates the intrinsic value of the Company's marketed products,
product pipeline, intellectual property and property, plant and equipment and
that, despite recent positive developments, this intrinsic value may not be
achieved under the multi-year strategic plan outlined by the Company in its

                                       6


public filings and in conversations with the Reporting Persons. Based on these
beliefs, and on what the Reporting Persons believe to be the Company's poor
execution in converting assets into shareholder value under current management
and inability or unwillingness to forecast a timeframe for the Company to
achieve positive operating cash flow and earnings, a representative of the
Management Company has advised the Company, in a series of telephone
conversations and meetings since February 2006, of the Reporting Persons' view
that the Company should immediately retain a new investment banking firm to
implement a strategic process aimed at maximizing stockholder value. The
Reporting Persons believe that this process should be conducted as publicly as
possible and should explore a sale of the Company in its entirety or otherwise,
as the Reporting Persons believe that there is significant interest in the
Company's assets under either scenario. A representative of the Management
Company has also advised the Company of the Reporting Persons' view that, during
the pendency of this process, the Company should refrain from selling or
partnering with respect to any of the Company's currently marketed or pipeline
products or other assets, unless any such sale or relationship would result in
extraordinary values that could be achieved in a strategic process.

     The Reporting Persons are engaged in the investment business. In pursuing
this business, the Reporting Persons analyze the operations, capital structure
and markets of companies, including the Company, on a continuous basis through
analysis of documentation and discussions with knowledgeable industry and market
observers and with representatives of such companies (often at the invitation of
management). From time to time, one or more of the Reporting Persons may hold
discussions with third parties or with management of such companies in which the
Reporting Person may suggest or take a position with respect to potential
changes in the operations, management or capital structure of such companies as
a means of enhancing shareholder value. Such suggestions or positions may relate
to one or more of the transactions specified in clauses (a) through (j) of Item
4 of Schedule 13D of the Exchange Act, including, without limitation, such
matters as disposing of or selling all or a portion of the company or acquiring
another company or business, changing operating or marketing strategies,
adopting or not adopting certain types of anti-takeover measures and
restructuring the company's capitalization or dividend policy.

     Except as set forth above, the Reporting Persons do not have any present
plans or proposals that relate to or would result in any of the actions required
to be described in Item 4 of Schedule 13D. Each of the Reporting Persons may, at
any time, review or reconsider its position with respect to the Company and
formulate plans or proposals with respect to any of such matters.


Item 5. Interest in Securities of the Issuer.

     (a) As of the date of this Schedule 13D, the Management Company
beneficially owns 5,000,000 shares of Common Stock. The Management Company
shares voting and dispositive power over such holdings with Mr. Loeb and with
the Funds. The Shares represent 8.4% of the 59,517,041 shares of Common Stock
outstanding as of March 24, 2006, as reported in the Schedule 14A filed by the
Company on April 7, 2006.

                                       7



     As of the date of this Schedule 13D, the Offshore Fund directly
beneficially owns 3,157,800 shares of Common Stock, which represent 5.3% of the
outstanding shares of Common Stock. None of the other individual Funds owns a
number of shares of Common Stock representing more than 5% of such total.

     (b) The Management Company and Mr. Loeb share voting and dispositive power
over the 5,000,000 shares of Common Stock held directly by the Funds. The
Management Company, Mr. Loeb and the Offshore Fund share voting power and
dispositive power over the 3,157,800 shares of Common Stock held by the Offshore
Fund.

     (c) Schedule A hereto sets forth certain information with respect to
transactions by the Funds, at the direction of the Reporting Persons, in the
Common Stock during the past 60 days.

     Schedule B hereto sets forth certain information with respect to
transactions by the Offshore Fund, at the direction of the Management Company
and Mr. Loeb, in the Common Stock during the past 60 days.

     All of the transactions set forth on Schedule A and Schedule B were
effected in the Nasdaq National Market.

     Except as set forth above and on Schedule A and Schedule B, during the last
60 days there were no transactions in the Common Stock effected by the Reporting
Persons, nor, to the best of their knowledge, any of their directors, executive
officers, general partners or members.

     (d) Other than the Funds which directly hold the Shares, and except as set
forth in this Item 5, no person is known to have the right to receive or the
power to direct the receipt of dividends from, or the proceeds from the sale of,
the Shares.

     (e) Not applicable.

Item 6. Contracts, Arrangements, Understandings or Relationships With Respect to
        Securities of the Issuer.

     Pursuant to Rule 13d-1(k) promulgated under the Exchange Act, the Reporting
Persons have entered into an agreement with respect to the joint filing of this
statement, and any amendment or amendments hereto.

     Except as set forth herein, there are no contracts, arrangements,
understandings or relationships among the persons named in Item 2 or between
such persons and any other person with respect to any securities of the Company.

                                       8



Item 7.  Material to be Filed as Exhibits.

     1. Joint Filing Agreement, dated as of April 17, 2006, by and between the
Reporting Persons.

                                       9




                                   Schedule A
                                   ----------

                   (Transactions by the Funds in Common Stock
                            during the past 60 days)


     Date        Transaction             Shares             Price Per Share($)
     ----        -----------             ------             ------------------

    2/24/06           BUY                100,000                   3.7845

    2/24/06           BUY                100,000                   3.8067

    2/24/06           BUY                 50,000                   3.7998

    2/27/06           BUY                 25,000                   3.9891

    2/27/06           BUY                 25,000                   3.9542

    3/7/06            BUY                200,000                   4.0555

    3/7/06            BUY                 85,000                   4.0914

    3/8/06            BUY                 15,000                   4.1017

    3/13/06           BUY                 80,000                   4.2488

    3/22/06           BUY                120,000                   5.3897

    3/22/06           BUY                 25,000                   5.3416

    3/23/06           BUY                 75,000                   5.3941

    3/24/06           BUY                 50,000                   5.53

    3/31/06           SELL                15,200                   5.63

    3/31/06           BUY                 15,200                   5.63

    4/5/06            BUY                100,000                   5.5261

    4/6/06            BUY                350,000                   5.5958

    4/7/06            BUY                385,000                   5.8428

    4/10/06           BUY                150,000                   5.7478

    4/11/06           BUY                200,000                   5.4963




    4/11/06           BUY                150,000                   5.5221

    4/12/06           BUY                200,000                   5.6139

    4/12/06           BUY                150,000                   5.6358

    4/13/06           BUY                150,000                   5.7938

    4/17/06           BUY                215,000                   5.6798




                                   Schedule B
                                   ----------

               (Transactions by the Offshore Fund in Common Stock
                            during the past 60 days)


     Date           Transaction            Shares           Price Per Share($)
     ----           -----------            ------           ------------------

    2/24/06              BUY                61,000                 3.7845

    2/24/06              BUY                62,800                 3.8067

    2/24/06              BUY                31,400                 3.7998

    2/27/06              BUY                15,700                 3.9891

    2/27/06              BUY                15,700                 3.9542

    3/7/06               BUY               125,600                 4.0555

    3/7/06               BUY                53,700                 4.0914

    3/8/06               BUY                11,200                 4.1017

    3/13/06              BUY                49,800                 4.2488

    3/22/06              BUY                73,800                 5.3897

    3/22/06              BUY                15,700                 5.3416

    3/23/06              BUY                49,300                 5.3941

    3/24/06              BUY                31,300                 5.53

    3/31/06              BUY                 7,800                 5.63

    4/5/06               BUY                62,500                 5.5261

    4/6/06               BUY               220,500                 5.5958

    4/7/06               BUY               242,200                 5.8428

    4/10/06              BUY                95,900                 5.7478

    4/11/06              BUY               126,100                 5.4963

    4/11/06              BUY                94,600                 5.5221




    4/12/06              BUY               129,300                 5.6139

    4/12/06              BUY                94,800                 5.6358

    4/13/06              BUY                94,800                 5.7938

    4/17/06              BUY               135,400                 5.6798




                                   SIGNATURES

     After reasonable inquiry and to the best of our knowledge and belief, the
undersigned certify that the information set forth in this statement is true,
complete and correct.


Dated: April 17, 2006


                                 THIRD POINT LLC



                                  By:  /s/ Daniel S. Loeb
                                       -----------------------------------------
                                        Name:  Daniel S. Loeb
                                        Title: Chief Executive Officer




                                  THIRD POINT OFFSHORE FUND, LTD.



                                   By:  /s/ Daniel S. Loeb
                                       -----------------------------------------
                                        Name:  Daniel S. Loeb
                                        Title: Director




                                   /s/ Daniel S. Loeb
                                   ---------------------------------------------
                                       Daniel S. Loeb




                 [SIGNATURE PAGE TO SCHEDULE 13D WITH RESPECT TO
                            NABI BIOPHARMACEUTICALS]


                                                           Exhibit 1
                                                           ---------

                             JOINT FILING AGREEMENT
                          PURSUANT TO RULE 13d-1(k)(1)
                          ----------------------------

     The undersigned acknowledge and agree that the foregoing statement on
Schedule 13D is filed on behalf of each of the undersigned and that all
subsequent amendments to this statement on Schedule 13D shall be filed on behalf
of each of the undersigned without the necessity of filing additional joint
filing agreements. The undersigned acknowledge that each shall be responsible
for the timely filing of such amendments, and for the completeness and accuracy
of the information concerning it contained therein, but shall not be responsible
for the completeness and accuracy of the information concerning the others,
except to the extent that it knows or has reason to believe that such
information is inaccurate. This Agreement may be executed in any number of
counterparts and all of such counterparts taken together shall constitute one
and the same instrument.

Dated: April 17, 2006


                                  THIRD POINT LLC



                                  By:  /s/ Daniel S. Loeb
                                       -----------------------------------------
                                        Name:  Daniel S. Loeb
                                        Title: Chief Executive Officer




                                  THIRD POINT OFFSHORE FUND, LTD.



                                   By:  /s/ Daniel S. Loeb
                                       -----------------------------------------
                                        Name:  Daniel S. Loeb
                                        Title: Director




                                   /s/ Daniel S. Loeb
                                   ---------------------------------------------
                                            Daniel S. Loeb



            [JOINT FILING AGREEMENT FOR SCHEDULE 13D WITH RESPECT TO
                            NABI BIOPHARMACEUTICALS]