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Date: March 17, 1995
FOR IMMEDIATE RELEASE
Contact:  Monica Revelle, PHS/FDA (301) 443-4177

FDA Licenses Chickenpox Vaccine

The Food and Drug Administration today announced the licensing of Varicella Virus Vaccine Live for the prevention of chickenpox, one of the most common childhood diseases. An estimated 3.7 million Americans are affected by chickenpox each year, with more than 90 percent of the cases occurring in persons under 15 years of age.

While highly contagious, chickenpox is generally mild and not normally life-threatening. However, some individuals, including adolescents and adults, are at higher risk of serious illness, and it is estimated that there are about 9,300 chickenpox-related hospitalizations and 50 to 100 deaths annually, most of which occur among young children.

"This vaccine has been studied in approximately 11,000 individuals, and we expect it to be 70 to 90 percent effective in preventing chickenpox," said FDA Commissioner David A. Kessler, M.D. "Furthermore, almost all of the vaccinated patients who got chickenpox had a milder form of the disease."

Chickenpox is transmitted to others through fluid from broken blisters as well as by coughing or sneezing. The average incubation period for chickenpox (the time between exposure to the virus and the onset of illness) is 10 to 21 days. A child is contagious from 1 or 2 days before the rash appears until all the lesions are dried -- usually 4 to 5 days.

A single injection of the vaccine is recommended for children ages 12 months to 12 years, while two injections 4 to 8 weeks apart are recommended for adolescents and adults -- ages 13 and older -- who have not contracted chickenpox. The vaccine has been shown to be safe and effective when administered at the same time as the measles, mumps and rubella vaccines.

Clinical trials of the vaccine were conducted over 10 years. Adverse reactions were mild and included redness, hardness and swelling at the injection site, fatigue, malaise and nausea.

In January 1994, the Vaccines and Related Biological Products Advisory Committee reviewed clinical data associated with safety and effectiveness of the vaccine. While the committee considered the vaccine safe and effective, it advised FDA to address several questions before a final decision on licensing could be made. These questions included long-term immunity, simultaneous administration with other vaccines, whether extensive inoculations in children would shift the disease to adults where it is more severe, and whether to give children one inoculation or two.

In January 1995, FDA presented clinical data to the committee that resolved those issues. FDA also informed the committee that the agency was working closely with the sponsor to resolve outstanding manufacturing and establishment issues.

The chickenpox vaccine is manufactured by Merck and Co. Inc., Whitehouse Station, N.J., under the trade name "Varivax." At FDA's request, Merck has agreed to perform postmarketing studies to determine the long-term effects of the vaccine and whether there is a need for a booster immunization.

FDA has approved the vaccine as effective when used according to the vaccine manufacturer's package insert, and physicians may use it as soon as the manufacturer makes it available. The Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices will publish recommendations on the vaccine's inclusion in the childhood immunization schedule this spring.

FDA and CDC are two of eight Public Health Service Agencies within HHS.

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