MERCK FILING ADDITIONAL VARIVAX DATA BASED ON LOTS MANUFACTURED AT NEW FACILITY
Merck will submit vaccination trial data on Varivax vaccine lots manufactured at its new facility to FDA by September. Merck filed a PLA for its chicken pox vaccine in August 1989; the product received a favorable review by FDA's Vaccines & Related Biological Products Advisory Committee on Jan. 25, 1990 ("The Pink Sheet" Jan. 29, 1990, T&G-7). Merck said in November that the Varivax review had at least a year to go. FDA is requiring the firm to study production lots of the live attenuated varicella vaccine from its new robotic facility, built expressly for Varivax production, before the product can be approved. The new tests began in December 1991. Merck Vaccine Division Clinical Research Director Jo White, MD, told the National Vaccine Advisory Committee's April 21 meeting that "we've vaccinated 1,900 children to date" with the new production lots. Overall, "we've vaccinated about 8,000 healthy patients and about 2,000 healthy adults." Results from trials of the new Varivax production lots show "no serious AEs [adverse events] related to vaccination," White said. The new production lots "are a little more potent than some of the lots used earlier." No efficacy data is available yet and "we are just beginning to get antibody titers" from the vaccines, White added. The Varivax PLA is seeking an indication for "children 12 months to 12 years of age, one dose, and for individuals 13 years and older, two doses, preferably two months apart," according to White. One of the FDA advisory committee's concerns had been the duration of protection afforded by Varivax. White told the committee that "95% of vaccinees still have antibody after six years." She also noted that, if exposed to varicella, these vaccinees' "antibody levels rise." White also presented data on an ongoing two-dose study in children. In "about 300 kids," researchers found a seroconversion rate after two doses of 97%, which is "about the same" as with one dose in earlier studies. She added, "we still have reported breakthrough cases in people even that get two doses" and "follow- up will continue." In single-dose studies published in 1984 and 1991, efficacy rates of 100% and 96% were reported, White said. In a household exposure efficacy trial, 18 of 114 (16%) developed chicken pox. White said this amounted to "a calculated efficacy of 82%." The Merck researcher said that the company's combination MMR and varicella vaccine, MMR II-V, "is in Phase III studies" and that Merck will file a PLA for the product "in summer of next year." Merck is also "looking at whether it's okay to give it [MMR II-V] to them together with OPV, DTP and flu vaccine [so] you can give several vaccinations at once."
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