Search

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.

Larvae from seven laboratory strains and eight isofemale lines of Drosophila melanogaster differ significantly with regard to their responses to light in a photokinesis assay in which the larvae are tested en masse. Larvae from the CA-2 laboratory stock fail to disperse on assay plates, although observations of individual CA-2 larvae suggest that the larvae are repelled by light. Larvae from all of the other laboratory stocks and all of the isofemale lines (except LI2 and NC5) avoid light in the photokinesis assay. Larvae from some stocks are much more strongly repelled by light than larvae from other stocks. LI2 larvae are unresponsive to light in most replicates of the photokinesis assay, while NC5 larvae are consistently unresponsive to light. Observations of F1 heterozygotes suggest that the allele(s) that affects the vision of LI2 and NC5 larvae has net effects on the animals' behavior that are partially dominant and recessive, respectively.