Although they are highly immunogenic, live attenuated cytomegalovirus (CMV) vaccines have the potential for latency, reactivation and oncogenicity. The feasibility of an inert subunit vaccine which mimics the immunogenic capacity of the live whole vaccine is therefore being investigated. The most promising vaccine candidates appear to be based on CMV glycoprotein B (gpB).Chiron Vaccines is developing a recombinant gpB subunit vaccine formulated in either alum or MF59, although MF59 appears to be the most effective adjuvant. US phase II trials of the vaccine have been completed and phase III trials are planned.Chiron had signed an agreement in principle with Univax Biologics covering the development of immunotherapeutics based on Chiron's vaccines. The first programme was to involve CMV immune globulin prepared from individuals immunised with the recombinant gpB/MF59 vaccine. Univax had intended to commence phase I/II trials with this product. However, Univax subsequently merged with Nabi and it is unclear if this agreement still exists.