FORM 6-K

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                        Report of Foreign Private Issuer

                    Pursuant to Rule 13s - 16 or 15d - 16 of
                      the Securities Exchange Act of 1934

                           For the month of November 2006


                                  Acambis plc
                (Translation of registrant's name into English)

                           Peterhouse Technology Park
                               100 Fulbourn Road
                               Cambridge CB1 9PT
                                    England

                    (address of principal executive offices)

    (Indicate by check mark whether the registrant files or will file annual
                 reports under cover of Form 20-F or Form 40-F

                         Forms 20-F X     Form 40-F

  Indicate by check mark whether the registrant by furnishing the information
     contained in this Form also thereby furnishing the information to the
                Commission pursuant to Rule 12g3-2(b) under the
                       Securities Exchange Act of 1934).

                              Yes       No X

 (if "Yes" is marked, indicate below the file number assigned to the registrant
                   in connection with Rule 12g3-2(b): 82- ).




Enclosure:

US Voluntary Delisting Update




Update on implementation of US voluntary delisting

Cambridge, UK and Cambridge, Massachusetts - 27 November 2006 - Acambis plc
("Acambis") (LSE: ACM; NASDAQ: ACAM) announces that it has given notice to the
NASDAQ Global Market that it intends voluntarily to delist its American
Depositary Shares ("ADSs"), effective on or about 18 December 2006, and has also
given notice to terminate its American Depositary Receipt ("ADR") facility,
effective as of the close of trading on 14 February 2007. This is in line with
the Acambis' announcement to delist and deregister made on 12 September 2006.

Acambis has notified the Bank of New York ("BNY"), the depositary for Acambis'
ADR facility, that it is terminating the facility, which will cause all
outstanding Acambis ADSs to be cancelled, and that the Registration Statement on
Form F-6 relating to Acambis' ADSs will be terminated.

In addition, the deposit agreement has been amended, with effect from 16
December 2006 to: (a) shorten from one year to 30 days the period of time that
must pass after termination of the deposit agreement before BNY may sell the
remaining deposited securities; and (b) change the provision on selling of
deposited securities after termination to require BNY to use reasonable efforts
to sell the remaining deposited securities after the specified period.

The deposit agreement will terminate on 14 February 2007, which is 90 days after
notice was issued to ADR holders. As a result of the amendment and termination
of the deposit agreement, ADR holders will have until 16 March 2007 to decide if
they would like to retain their interest in Acambis' shares. If they do not
surrender their ADRs and request delivery of the underlying Acambis shares, they
will lose the right to receive those shares and, instead, will be entitled, upon
subsequent surrender of their ADRs, to receive the net proceeds of sale of those
shares. The date or dates on which BNY will sell remaining deposited shares will
be no earlier than 19 March 2007.

ADR holders can contact BNY for further information on telephone number
+1-888-BNY-ADRS (1-888-269-2377).

Acambis has also given notice to NASDAQ that it intends to delist the Company's
ADSs. Pursuant to this notice, the Company intends to file a Form 25 with the
Securities and Exchange Commission ("SEC") on or about 7 December 2006 to remove
the Company's ADSs from listing. The removal should be effective ten days after
the filing of the Form 25. According to this schedule, the last day for trading
the Company's ADSs on NASDAQ will be 18 December 2006.

Acambis' continuing commitment to its US operations is not affected by its
decision to withdraw its ADS listing from NASDAQ. Acambis' total number of
shares outstanding and the listing of its ordinary shares on the London Stock
Exchange will not be affected by the planned actions.

                                     -ends-

Enquiries:

Acambis plc
Lyndsay Wright, VP, Communications and IR
Tel: +44 (0 1223 275 300

Financial Dynamics
David Yates/Anna Keeble
Tel: +44 (0) 20 7831 3113

About Acambis

Acambis is a leading biotechnology company targeting infectious diseases with
novel vaccines. Acambis' development-stage pipeline includes vaccines that could
either offer improvements over existing products or target unmet medical needs.
Its investigational vaccine against Japanese encephalitis, ChimeriVax-JE, which
is undergoing Phase 3 clinical testing, is intended to provide an "ideal"
vaccine to address the estimated 50,000 cases of this viral disease in Asia
every year. Acambis' proprietary ChimeriVax technology, developed in association
with St Louis University, has also been used to develop ChimeriVax-West Nile,
which is undergoing Phase 2 clinical testing, making it the most advanced
investigational vaccine against the West Nile virus. Acambis also has the only
vaccine in development against Clostridium difficile bacteria, a leading cause
of hospital-acquired infections. Recognised internationally as the leading
producer of smallpox vaccines, Acambis is developing an investigational smallpox
vaccine, ACAM2000, and is manufacturing emergency-use stockpiles of this
investigational vaccine for the US Government and other governments around the
world. It is also developing an attenuated smallpox vaccine, MVA3000, under
contracts with the US National Institutes of Health.

Acambis is based in Cambridge, UK and Cambridge, Massachusetts, US, and is
listed on the London Stock Exchange (ACM). Its shares are listed on NASDAQ
(ACAM) in the form of American Depositary Receipts. More information is
available at www.acambis.com.

"Safe Harbor" statement under the Private Securities Litigation Reform Act of
1995:

The statements in this news release that are not historical facts are
forward-looking statements that involve risks and uncertainties, including the
Company's plans voluntarily to delist its ADSs from NASDAQ and to terminate its
ADR facility, the timing and results of clinical trials, product development,
manufacturing and commercialisation risks, the risks of satisfying the
regulatory approval process in a timely manner, the need for and the
availability of additional capital. For a discussion of these and other risks
and uncertainties see "Risk management" in the Company's 2005 Annual Report and
"Risk factors" in its Form 20-F, in addition to those detailed on the Company's
website and in the Company's filings made with the Securities and Exchange
Commission from time to time. These forward-looking statements are based on
estimates and assumptions made by the management of Acambis and are believed to
be reasonable, though are inherently uncertain and difficult to predict. Actual
results or experience could differ materially from the forward-looking
statements.












                                      SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant Peptide Therapeutics Group has duly caused this report to be
signed on its behalf by the undersigned, thereunto duly authorized.



Date: 27 November, 2006                       ACAMBIS PLC





                                        By:  /s/ Lyndsay Wright
                                             Name: Lyndsay Wright
                                             Title: VP, Communications and IR.