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. " v:shapes="_x0000_s1026">