Immunisation "Green Book"
The current edition of the Green Book will be found at  as long as sense prevails in government websites. It is now possible to sign up to receive emails when updates are made.
The previous edition - 'Immunisation Against Infectious Disease 2006 - "The Green Book"' was published in December 2006.
(Vaccine Update newsletters for UK should be available here.)
Vaccination policy evolves as more evidence becomes available, and as new vaccines are developed. Policy is changed via official letters from the Department of Health in England, and the competent bodies in other administrations, usually based on advice from the Joint Committee on Vaccination and Immunisation (JCVI) (although political considerations may also apply). In England these letters come from the chief medical officer, the chief nursing officer, and the chief pharmaceutical officer.
Fortunately, not only can the most recent edition of the Green Book be accessed via the above web sites, but the DH site also has revised chapters, and late-draft versions of new chapters. Revised chapters are often marked as "draft". They are, nevertheless, generally considered to be the current policy.
The previous hard copy edition, 'Immunisation Against Infectious Disease 1996 - "The Green Book"' was published in 1996 by: Department of Health (England), Welsh Office, Scottish Office Department of Health, and DHSSPS Northern Ireland. (NB - some of these bodies have now evolved; links are to their (November 2005) incarnation.)