文本框: MMRV: Progress to date Steens J-M GlaxoSmithKline, Rixensart, Belgium A tetravalent measles–mumps–rubella–varicella (MMRV) vaccine would facilitate the implementation of universal immunization against varicella in early childhood. The successful development of a new MMR vaccine (PriorixÔ; GSK) using RIT 4385, a Jeryl Lynn-derived mumps vaccine strain, and of a thermostable reformulation of VarilrixÔ (GSK), an OKA strain-based varicella vaccine, have paved the way for the development of a combined MMRV vaccine. In a randomized study in children in their second year of life, the reactogenicity and immunogenicity of this candidate MMRV vaccine have shown results which are similar to those observed after the simultaneous administration of PriorixÔ and VarilrixÔ in opposite arms. There was a slight increase (4.4%) in the cumulative incidence of rectal temperatures of >39.5°C in the MMRV group during the 6-week observation period, a clinically acceptable difference in view of the advantages of a single over two injections. Seroconversion rates against each of the viruses in the tetravalent and the licensed trivalent and monovalent vaccines were comparable (>96%). These encouraging results led to the initiation of a large Phase III clinical studies program including over 6000 subjects worldwide.