These results indicated the comparability of immune responses to mumps elicited by MMRV and MMR+V vaccines. of non-inferiority in mumps SCRs was consequently not met, although the observed group difference in apost-hocanalysis of anti-mumps antibodies using a plaque reduction neutralization assay was 0.39% having a 95% CI reduce limit of -4.03%. Adverse events PDK1 occurred at similar frequencies for both organizations, except for more frequent fever in MMRV recipients. == Summary == Based on the pre-specified non-inferiority criterion, SCRs of the MMRV vaccine were non-inferior to that elicited by MMR+V vaccines for those antigens except mumps. Keywords:Immunogenicity, Security, Plaque reduction assay, Measles-mumps-rubella-varicella vaccine, Korea == Intro == Measles, mumps, rubella and varicella are four common and potentially severe infectious diseases in children worldwide [1-3]. Complications associated with these diseases can be severe and potentially life-threatening [1-4]. Measles and varicella are associated with severe complications leading to hospitalizations and potentially death [1,4]. Mumps generally causes severe forms of meningitis and encephalitis [2]. Infants given birth to to women infected with rubella in their 1st trimester of pregnancy are at high risk of congenital rubella syndrome, which may result in death [3,4]. In Korea, since the introduction of a combined measles-mumps-rubella (MMR) vaccine in the national immunization program, the morbidity and mortality associated with these diseases offers decreased considerably [5]. Measles removal was accomplished in Korea in 2006 [6] and CDK8-IN-1 reported rubella instances decreased from 2001 to 2009 [7]. On the other hand, while immunization did result in a considerable decrease in mumps instances, a resurgence of mumps was observed between 2003 and 2009 [5]. Furthermore, although a varicella vaccine has been routinely given to children (age, 12 to 15 weeks) since 2005, the seroprevalence of varicella continues to be relatively high (50% in children aged 1-2 years, 75% in children aged 5-6 years and 90% in individuals aged >11 years) [8]. A live-attenuated MMR vaccine, Priorix (GlaxoSmithKline, Rixensart, Belgium) and a live-attenuated varicella vaccine, Varilrix (GlaxoSmithKline) have been available since 1997 and 1994, respectively [9]. Both vaccines are recommended by the United States Center for Disease Control’s (CDC) Advisory Committee on Immunization Methods (ACIP) as two doses each, with related schedules (1st dose at 12-15 weeks and the second dose at 4-6 years) [10,11]. These vaccines were found to be well tolerated when given concomitantly as independent injections, and don’t appear to adversely interfere with the immunogenicity of any of the vaccine antigens [12]. Considering the related vaccination schedules for both vaccines, a combined tetravalent MMR-varicella (MMRV) vaccine that would confer safety against all four diseases was developed (Priorix-Tetra, GlaxoSmithKline). The combined MMRV vaccine is based on the licensed MMR and varicella vaccines [9] and would allow for more flexibility in incorporating the vaccine into the increasing quantity of scheduled child years vaccinations [9,13-18]. Results from earlier clinical studies have shown similar immunogenicity and tolerability between the combined MMRV vaccine and concomitant administrations of the MMR CDK8-IN-1 and varicella vaccines [9]. In several European countries, the combined MMRV vaccine is definitely licensed for use relating to a two-dose routine in babies aged 9 weeks, with a minimum interval of six weeks between doses [15]. In the present study, the immunogenicity and security of a single dose of a combined MMRV vaccine in comparison to that of concomitant administrations of MMR and varicella vaccines given as separate injections was assessed in healthy Korean children during their second 12 months of existence. == Materials and Methods == == Study design and subjects == This was a phase IIIb, open-labeled, randomized study (NCT00751348) carried out at 13 study centers in South Korea between October 2008 and May 2010. Healthy children aged 11-24 weeks, not previously immunized against measles, mumps, rubella and/or varicella and without a earlier history of these diseases were randomized into two parallel treatment organizations (2:1) to receive either one dose of the combined MMRV vaccine (MMRV group) or MMR and varicella vaccines concomitantly as independent injections (MMR+V group). Subjects were excluded from participating in the study if they experienced received any investigational drug or vaccine 30 days before the CDK8-IN-1 administration of the study vaccine, if they experienced received immunosuppressants, immunoglobulins or any blood products six months prior to the study, if they experienced a history of allergy likely to be aggravated by any of the vaccine parts, chronic illness or family.