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Background: Administration of M-M-R II (Measles, Mumps and Rubella Virus Vaccine, Live) and VARIVAX [Varicella Virus Vaccine Live (Oka/Merck)] given concomitantly at separate injection sites during the same office visit could increase vaccine compliance by reducing the number of health care visits for immunizations. We compared the safety and immunogenicity of M-M-R II and VARIVAX given concomitantly at separate sites (Group A) with administration of the two vaccines 6 weeks apart (Group B) as well as the persistence of varicella antibody and the duration of protection afforded by varicella vaccine., Methods: A total of 603 healthy children, ages 12 months to 6 years, with no history of measles, mumps, rubella, varicella and zoster or vaccination against these diseases, were randomized to either Group A or B and were followed for clinical reactions and serologic responses to all four viral components. Children were enrolled from August through December, 1993. Subjects were followed for 5 years to evaluate persistence of varicella antibody and breakthrough varicella rates. We compared breakthrough rates to expected attack rates in unvaccinated children to produce estimates of vaccine efficacy., Results: Both vaccine regimens were generally well-tolerated. There were no significant differences between the groups in the rates of fever, injection site reactions or rashes after vaccination. Seroconversion rates and geometric mean titers for measles, mumps and rubella were not significantly different between groups. The varicella seroconversion rate and percentage with glycoprotein-based ELISA titers > or = 5.0 units were similar between the two groups (99.5 and 92.5% vs. 100 and 94.8% for Groups A and B, respectively), but the geometric mean titers were statistically significantly different (13.2 for Group A and 17.9 for Group B). Varicella antibody persistence rates were >98 to 100% during 6 years of follow-up in both groups. Compared with historical rates, varicella vaccine efficacy during 5 years was estimated to be 90.5% (95% confidence interval, 86.2%, 95.0%) and 88.9% (95% confidence interval, 83.7%, 93.7%) in Groups A and B, respectively., Conclusions: Administration of M-M-R II and VARIVAX concomitantly at separate injection sites or 6 weeks apart was generally well-tolerated and immunogenic in healthy children 12 months to 6 years of age. VARIVAX administered with M-M-R II induced persistent immunity and long-term protection against breakthrough varicella infection.

Background: We used the large clinical database that supported the development of Oka/ Merck varicella vaccine to study the relationship between the primary varicella antibody response, as determined by gpELISA, an enzyme-linked immunosorbent assay that detects antibodies to varicella-zoster virus (VZV) glycoprotein, and the subsequent risk of postvaccination breakthrough varicella., Methods: We vaccinated 1,164 healthy children with a single dose of varicella vaccine containing 2900 to 9000 plaque-forming units/dose. The primary immune response to vaccination was determined by gpELISA 6 weeks after vaccination. Subjects were followed annually for 7 years to ascertain cases of breakthrough varicella., Results: The estimated vaccine efficacy among children with a 6-week postvaccination antibody titer of > or = 5 gpELISA units was 95.5% (95% confidence interval, 94.2%, 96.8%) compared with 83.5% (95% confidence interval, 76.9%, 89.5%) for subjects with a titer of <5 gpELISA units. Children with a 6-week postvaccination antibody titer of <5 gpELISA units were 3.5 times more likely than those with a titer of > or = 5 gpELISA units to develop breakthrough varicella., Conclusions: We identified a 6-week postvaccination antibody titer of > or = 5 gpELISA units as an approximate correlate of protection. In addition we established an accelerated failure time model based on log normal hazard that predicted varicella breakthrough rates based on the distribution of 6-week postvaccination varicella antibody titers.

Objective: To document the duration of protection afforded by Oka/Merck varicella vaccine over a 7-year period., Study Design: The subjects were healthy children 1 to 12 years of age originally enrolled in clinical studies to evaluate the primary immune response to varicella vaccine 6 weeks after vaccination. Each was monitored for antibody persistence, breakthrough infection, and household exposure to varicella to produce estimates of vaccine efficacy., Results: The 6-year cumulative varicella antibody persistence rate was 99.5% (95% CI: 98.9%, 100.0%). The annual breakthrough rate through 7 years ranged from 0.2% to 2.3% per year; the estimated cumulative event rate was 6.5%. Comparison of the observed average annual breakthrough rate with the age-adjusted expected annual incidence rate of varicella in unvaccinated children corresponded to an estimated vaccine efficacy of 93.8% to 94.6%. Eighty vaccinated children were exposed to varicella in the household, resulting in 8 (10%) cases of infection. When compared with the historical attack rate of 86.8% in unvaccinated susceptible persons exposed to varicella in the household, this yields an estimated vaccine efficacy of 88.5% (95% CI: 80.9%, 96.1%). Varicella cases in vaccinated children generally were mild., Conclusion: The live attenuated varicella vaccine is highly effective in inducing persistent immunity and long-term protection against breakthrough varicella infection.