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                            VANGUARD(R) PRIMECAP FUND
              SUPPLEMENT TO THE PROSPECTUS DATED DECEMBER 12, 2003

IMPORTANT CHANGES TO VANGUARD PRIMECAP FUND

FUND CLOSED TO NEW SHAREHOLDERS
Effective as of the close of business on March 4, 2004,  Vanguard  PRIMECAP Fund
will no longer accept new shareholders, and will limit additional investments by
existing  shareholders  as further  described  below.  There is no specific time
frame for when the Fund will reopen.

Existing  shareholders  of Vanguard  PRIMECAP  Fund may invest up to $25,000 per
year in the Fund during the closed  period.  This $25,000  limit  applies to the
total amount invested  during any calendar year in all Fund accounts  registered
to  the  same  primary  Social  Security  or  taxpayer   identification  number.
Investments  made on or before March 4, 2004,  will not count toward the $25,000
annual limit, nor will dividend and capital gains reinvestments. Participants in
certain qualified retirement plans may continue to invest in accordance with the
terms of their plans.  Certain qualifying asset allocation programs may continue
to operate in accordance with their program terms.

ELECTRONIC TRANSACTIONS
During the closed period,  it will not be possible to purchase Vanguard PRIMECAP
Fund shares through Vanguard's website or Tele-Account(R) service. Shareholders,
however, may continue to redeem Fund shares using these electronic methods.

Vanguard PRIMECAP Fund may modify these transaction policies at any time without
advance  notice  to  shareholders.   Please  call  Vanguard  for  more  detailed
information about the Fund's transaction  policies.  Investors in non-retirement
accounts and IRAs should call  Vanguard's  Investor  Information  Department  at
1-800-662-7447.  Participants in employer-sponsored retirement plans should call
Vanguard Participant Services at 1-800-523-1188.




(C)2004 The Vanguard Group, Inc. All rights reserved.
Vanguard Marketing Corporation, Distributor.                         PS59 032004