<PAGE>   1

     As filed with the Securities and Exchange Commission on July 31, 1998.
                                                Registration No. 333- __________

--------------------------------------------------------------------------------


                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8

                             REGISTRATION STATEMENT
                                    UNDER THE
                             SECURITIES ACT OF 1933


                                  ORAVAX, INC.
--------------------------------------------------------------------------------
               (Exact name of issuer as specified in its charter)


            Delaware                                    04-3085209
-------------------------------             ------------------------------------
(State or other jurisdiction of             (I.R.S. Employer Identification No.)
incorporation or organization)


38 Sidney Street, Cambridge, Massachusetts                 02139
--------------------------------------------------------------------------------
 (Address of Principal Executive Offices)               (Zip Code)


                        1995 EMPLOYEE STOCK PURCHASE PLAN
--------------------------------------------------------------------------------
                            (Full Title of the Plan)


                           John M. Westcott, Jr., Esq.
                              c/o Hale and Dorr LLP
                                 60 State Street
                           Boston, Massachusetts 02109
--------------------------------------------------------------------------------
                     (Name and Address of Agent for Service)


                                 (617) 526-6000
--------------------------------------------------------------------------------
          (Telephone Number, Including Area Code, of Agent For Service)




<PAGE>   2



                         CALCULATION OF REGISTRATION FEE


================================================================================
                                      Proposed      Proposed
 Title of                              Maximum       Maximum
Securities              Amount        Offering      Aggregate         Amount
  to be                 to be         Price Per     Offering     of Registration
Registered            Registered      Share (1)     Price (1)          Fee
--------------------------------------------------------------------------------
Common Stock,
$.001 par value     125,000 shares     $0.9844      $123,050           $37
================================================================================

(1)      Estimated solely for the purpose of calculating the registration fee
         pursuant to Rule 457(c) and (h) and based on the average of the
         reported high and low sale prices of the registrant's Common Stock on
         the Nasdaq National Market on July 24, 1998.



                                        2


<PAGE>   3



                     STATEMENT OF INCORPORATION BY REFERENCE

         This Registration Statement on Form S-8 (the "Registration Statement")
incorporates by reference the contents of the Registration Statement on Form
S-8, File No. 33-94990, filed by OraVax, Inc., a Delaware corporation (the
"Company"), with the Securities and Exchange Commission on July 26, 1995,
relating to the Company's 1995 Employee Stock Purchase Plan.







                                        3


<PAGE>   4



                                   SIGNATURES


         Pursuant to the requirements of the Securities Act of 1933, the Company
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Boston, Commonwealth of Massachusetts, on the 31st
day of July, 1998.

                                             ORAVAX, INC.


                                             By: /s/ Lance K. Gordon
                                                 -------------------------------
                                                 Lance K. Gordon,
                                                 President and
                                                 Chief Executive Officer


                                POWER OF ATTORNEY

         We, the undersigned Directors and Officers of the Company hereby
constitute Lance K. Gordon, Brigid A. Makes and John M. Westcott, Jr., and each
of them singly, our true and lawful attorneys with full power to them, and each
of them singly, to sign for us and in our names in the capacities indicated
below, the Registration Statement on Form S-8 filed herewith and any and all
subsequent amendments to said Registration Statement, and generally to do all
such things in our names and behalf in our capacities as Directors and Officers
to enable OraVax, Inc. to comply with all requirements of the Securities Act of
1933, as amended, and all requirements of the Securities and Exchange
Commission, hereby ratifying and confirming our signatures as they may be signed
by said attorneys, or any of them, to said Registration Statement and any and
all amendments thereto.

         Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacities and on the dates indicated.



                                        4


<PAGE>   5




Signature                             Title                      Date
---------                             -----                      ----

(i)      Principal executive                                     )
         officer:                                                )
                                                                 )
                                                                 )
/s/ Lance K. Gordon                   President and              )
----------------------------------    Chief Executive            )
Lance K. Gordon                       Officer                    )
                                                                 )
(ii)     Principal financial and                                 )
         accounting officer:                                     )
                                                                 )
                                                                 )
/s/ Brigid A. Makes                   Vice President, Finance    )
----------------------------------    and Chief Financial        )
Brigid A. Makes                       Officer                    )
                                                                 )
(iii)    A majority of the                                       )
         Board of Directors:                                     )
                                                                 )
                                                                 )
/s/ Lance K. Gordon                   Director                   ) July 31, 1998
----------------------------------                               )
Lance K. Gordon                                                  ) 
                                                                 )
                                                                 )
/s/ C. Boyd Clarke                    Director                   )
----------------------------------                               )
C. Boyd Clarke                                                   )
                                                                 )
                                                                 )
/s/ Andre L. Lamotte                  Director                   )
----------------------------------                               )
Andre L. Lamotte                                                 )
                                                                 )
                                                                 )
/s/ Douglas MacMaster                 Director                   )
----------------------------------                               )
Douglas MacMaster                                                )
                                                                 )
                                                                 )
/s/ Allen Misher                      Director                   )
----------------------------------                               )
Allen Misher                                                     )
                                                                 )


                                        5


<PAGE>   6



                                  EXHIBIT INDEX



Exhibit No.                        Description                         Page
-----------                        -----------                         ----

  4.1*            Second Amended and Restated Certificate               --
                  of Incorporation of the Registrant.

  4.2*            Amended and Restated By-Laws of the                   --
                  Registrant

  5.1             Opinion of Hale and Dorr LLP.                          6

  23.1            Consent of PricewaterhouseCoopers LLP                  8

  23.2            Consent of Hale and Dorr LLP (included in              6
                  Exhibit 5.1).

  24              Power of Attorney (included on page                    3
                  3 of this Registration Statement).








---------

    *    Incorporated herein by reference to the Company's Registration
         Statement on Form S-1, as amended (File No. 33-90936).
[{"type": "S-8", "sequence": "1", "description": "ORAVAX, INC.", "secsgml_size_bytes": 9780}]
{"company-data": {"conformed-name": "ORAVAX INC /DE/", "cik": "0000900122", "assigned-sic": "2836", "irs-number": "043085209", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-60299", "film-number": "98675142"}, "business-address": {"street1": "38 SIDNEY ST 4TH FLOOR", "city": "CAMBRIDGE", "state": "MA", "zip": "02139", "phone": "6175266000"}}
1

     As filed with the Securities and Exchange Commission on July 31, 1998.
                                                Registration No. 333- __________

--------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8

                             REGISTRATION STATEMENT
                                    UNDER THE
                             SECURITIES ACT OF 1933

                                  ORAVAX, INC.
--------------------------------------------------------------------------------
               (Exact name of issuer as specified in its charter)

            Delaware                                    04-3085209
-------------------------------             ------------------------------------
(State or other jurisdiction of             (I.R.S. Employer Identification No.)
incorporation or organization)

38 Sidney Street, Cambridge, Massachusetts                 02139
--------------------------------------------------------------------------------
 (Address of Principal Executive Offices)               (Zip Code)

                        1995 EMPLOYEE STOCK PURCHASE PLAN
--------------------------------------------------------------------------------
                            (Full Title of the Plan)

                           John M. Westcott, Jr., Esq.
                              c/o Hale and Dorr LLP
                                 60 State Street
                           Boston, Massachusetts 02109
--------------------------------------------------------------------------------
                     (Name and Address of Agent for Service)

                                 (617) 526-6000
--------------------------------------------------------------------------------
          (Telephone Number, Including Area Code, of Agent For Service)
2

                         CALCULATION OF REGISTRATION FEE

================================================================================
                                      Proposed      Proposed
 Title of                              Maximum       Maximum
Securities              Amount        Offering      Aggregate         Amount
  to be                 to be         Price Per     Offering     of Registration
Registered            Registered      Share (1)     Price (1)          Fee
--------------------------------------------------------------------------------
Common Stock,
$.001 par value     125,000 shares     $0.9844      $123,050           $37
================================================================================

(1)      Estimated solely for the purpose of calculating the registration fee
         pursuant to Rule 457(c) and (h) and based on the average of the
         reported high and low sale prices of the registrant's Common Stock on
         the Nasdaq National Market on July 24, 1998.

                                        2
3

                     STATEMENT OF INCORPORATION BY REFERENCE

         This Registration Statement on Form S-8 (the "Registration Statement")
incorporates by reference the contents of the Registration Statement on Form
S-8, File No. 33-94990, filed by OraVax, Inc., a Delaware corporation (the
"Company"), with the Securities and Exchange Commission on July 26, 1995,
relating to the Company's 1995 Employee Stock Purchase Plan.

                                        3
4

                                   SIGNATURES

         Pursuant to the requirements of the Securities Act of 1933, the Company
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Boston, Commonwealth of Massachusetts, on the 31st
day of July, 1998.

                                             ORAVAX, INC.

                                             By: /s/ Lance K. Gordon
                                                 -------------------------------
                                                 Lance K. Gordon,
                                                 President and
                                                 Chief Executive Officer

                                POWER OF ATTORNEY

         We, the undersigned Directors and Officers of the Company hereby
constitute Lance K. Gordon, Brigid A. Makes and John M. Westcott, Jr., and each
of them singly, our true and lawful attorneys with full power to them, and each
of them singly, to sign for us and in our names in the capacities indicated
below, the Registration Statement on Form S-8 filed herewith and any and all
subsequent amendments to said Registration Statement, and generally to do all
such things in our names and behalf in our capacities as Directors and Officers
to enable OraVax, Inc. to comply with all requirements of the Securities Act of
1933, as amended, and all requirements of the Securities and Exchange
Commission, hereby ratifying and confirming our signatures as they may be signed
by said attorneys, or any of them, to said Registration Statement and any and
all amendments thereto.

         Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacities and on the dates indicated.

                                        4
5

Signature                             Title                      Date
---------                             -----                      ----

(i)      Principal executive                                     )
         officer:                                                )
                                                                 )
                                                                 )
/s/ Lance K. Gordon                   President and              )
----------------------------------    Chief Executive            )
Lance K. Gordon                       Officer                    )
                                                                 )
(ii)     Principal financial and                                 )
         accounting officer:                                     )
                                                                 )
                                                                 )
/s/ Brigid A. Makes                   Vice President, Finance    )
----------------------------------    and Chief Financial        )
Brigid A. Makes                       Officer                    )
                                                                 )
(iii)    A majority of the                                       )
         Board of Directors:                                     )
                                                                 )
                                                                 )
/s/ Lance K. Gordon                   Director                   ) July 31, 1998
----------------------------------                               )
Lance K. Gordon                                                  ) 
                                                                 )
                                                                 )
/s/ C. Boyd Clarke                    Director                   )
----------------------------------                               )
C. Boyd Clarke                                                   )
                                                                 )
                                                                 )
/s/ Andre L. Lamotte                  Director                   )
----------------------------------                               )
Andre L. Lamotte                                                 )
                                                                 )
                                                                 )
/s/ Douglas MacMaster                 Director                   )
----------------------------------                               )
Douglas MacMaster                                                )
                                                                 )
                                                                 )
/s/ Allen Misher                      Director                   )
----------------------------------                               )
Allen Misher                                                     )
                                                                 )

                                        5
6

                                  EXHIBIT INDEX

Exhibit No.                        Description                         Page
-----------                        -----------                         ----

  4.1*            Second Amended and Restated Certificate               --
                  of Incorporation of the Registrant.

  4.2*            Amended and Restated By-Laws of the                   --
                  Registrant

  5.1             Opinion of Hale and Dorr LLP.                          6

  23.1            Consent of PricewaterhouseCoopers LLP                  8

  23.2            Consent of Hale and Dorr LLP (included in              6
                  Exhibit 5.1).

  24              Power of Attorney (included on page                    3
                  3 of this Registration Statement).

---------

    *    Incorporated herein by reference to the Company's Registration
         Statement on Form S-1, as amended (File No. 33-90936).