Chickenpox Complications May Be Serious Scientists Report At CDC Immunization Conference

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DETROIT, May 21, 1997 - The following was released today by Merck & Co. (NYSE: MRK):

Chickenpox, often thought of as an annoying, but relatively benign childhood illness, too often may lead to hospitalization or even death, researchers reported today at the 31st National Immunization Conference sponsored by the Centers for Disease Control National Immunization Program. The reports follow an alert on Varicella (chickenpox) Mortality in the May 16 issue of the CDC's Morbidity and Mortality Weekly Report (MMWR).

Surveillance Data

"Data from active surveillance sites in the United States indicate that chickenpox is still actively occurring in these communities," said Dr. Jane Seward, CDC epidemiologist. "One of the challenges facing public health professionals is to educate the public and health-care providers that chickenpox is not an entirely benign disease. There are approximately 100 deaths and 9,300 hospitalizations due to complications of chickenpox each year. The majority of these deaths and complications occur in previously healthy individuals, and should be preventable by vaccination," Dr. Seward said. Chickenpox can be complicated by a variety of serious conditions including skin infections which can progress to blood borne infections, infections of the brain which may result in disability, and serious pneumonia. In rare incidences, these complications can progress to death.

Because chickenpox is one of the most contagious infectious diseases in the U.S. with approximately 4 million cases a year, there are challenges to establishing surveillance programs. The CDC commissioned three community- based surveillance programs to more accurately monitor the incidence, complications, and prevention of chickenpox. Programs are underway in Philadelphia; Austin, Texas; and Los Angeles. Among the key findings to date:

• In an inner-city population in west Philadelphia, the hospitalization rate for complications of chickenpox was seven times greater than predicted using the estimated national incidence rate of 9,300 hospitalizations per year.
  
  
• In Austin, Texas, the incidence of chickenpox has substantially declined since the licensure of the vaccine to prevent chickenpox in 1995. The decrease in chickenpox incidence was most significant (63 percent decrease) in preschool-age children where there has been widespread immunization efforts in the private sector among daycare attendees.
  
  
• In Los Angeles, where the first year of surveillance of Antelope Valley residents has been completed, 7,222 cases of chickenpox occurred among two to 18-year-olds according to surveillance estimates. Most recently, the surveillance project reported the death of an 18-month- old child from chickenpox complicated by toxic streptococcal disease.
  
  

Daycare

Researchers also presented data from studies on the use of the chickenpox vaccine in daycare attendees. Schools and daycare centers report the largest numbers of outbreaks of chickenpox due to the large numbers of susceptible children in close contact with each other. The chickenpox virus is easily spread from person to person by direct contact, or through the air. In a household or daycare center, nine-out-of-ten of the susceptible children exposed to a child with chickenpox will contract the disease. A number of studies in daycare attendees are underway:

• As part of its post-licensure surveillance program on the chickenpox vaccine, Merck & Co., Inc. is sponsoring a Duke University Department of Pediatrics study to assess the changing epidemiology of chickenpox among 1,200 children in 10 daycare centers. Preliminary findings indicate that the chickenpox vaccine is generally well-tolerated and demonstrates protective efficacy. No vaccine-related serious adverse events have been reported in the study. There have been no cases of chickenpox detected among vaccinees in the first year of the study, while the chickenpox rate in the unvaccinated populations in the study was significant (range among centers 1.4 percent to 83.9 percent with an average of 13.7 percent).
  
  
• A chickenpox outbreak at a daycare center in Atlanta provided CDC epidemiologists an opportunity to study the effectiveness of the vaccine. "Among children who had not been vaccinated prior to the outbreak, 88 percent of the children contracted chickenpox," said Dr. Seward. "Among those who had been vaccinated, only 14 percent developed chickenpox and in all cases the disease was mild."
  
  

Clinical Studies

Also at the conference Merck researchers presented data on long-term immunity and safety studies. More than a decade of clinical research went into the development of the chickenpox vaccine and overall 9,454 healthy children and 1,648 healthy adolescents and adults were vaccinated in clinical trials. "We continue to monitor the safety and effectiveness of the vaccine in the marketed environment where it has been given to more that 5 million individuals," said Dr. Robert Sharrar, senior director, Vaccine Safety, Merck Research Laboratories. "So far, we have not seen any evidence of waning immunity and the adverse experiences are similar to those observed in clinical trials." In clinical studies the most frequently reported reactions following vaccination in healthy children were injection site complaints such as pain, redness or swelling (19.35 percent); fever (14.7 percent) and mild varicella- like rash (7.2 percent local and generalized). Other reactions post- vaccination have been reported. These are detailed in the attached full prescribing information. A causal relationship to vaccination has not been established. In clinical studies immune response persistence has been demonstrated for five years post-vaccination. A boost in antibody levels has been observed in vaccinees following exposure to natural chickenpox. The duration of protection from chickenpox in the absence of wild-type boosting is unknown at present.

Vaccine Use Increasing

The chickenpox vaccine, marketed as VARIVAX(R) by Merck & Co., Inc., was licensed by the U.S. Food & Drug Administration in March 1995 and is now available to the public sector through the Vaccines For Children's Program. "Uptake of the vaccine has been steadily increasing," says Dr. Thomas Vernon, executive director Scientific and Public Health Policy, Merck Vaccine Division. "To date, more than 6 million doses of the vaccine have been distributed. Our research indicates that in the private sector immunization rates for the one to two-year old cohort are approaching 70 percent, while in the public sector all but three states have ordered the vaccine for use in their immunization programs." The chickenpox vaccine has been approved for use among healthy individuals 12 months of age and older. The CDC's Advisory Committee on Immunization Practices, the American Academy of Pediatrics and the American Academy of Family Physicians recommend that:

• all healthy children be routinely vaccinated at 12-18 months of age.
  
  
• children 19 to 12 years of age who have not had chickenpox should be vaccinated. After 12 years of age, natural chickenpox is more severe and complications are more frequent.
  
  
• adolescents and adults should be assessed for immune status and those who are susceptible to chickenpox should be vaccinated. Because natural chickenpox can be severe in older adolescents and adults, immunity is desirable in these groups.
  
  

Certain individuals should not receive the vaccine, including those with a history of hypersensitivity or an anaphylactic reaction to any component of the vaccine including gelatin and neomycin, or with any immunodeficient condition, or receiving immunosuppressive therapy. The vaccine should not be administered during pregnancy and pregnancy should be avoided for three months following vaccination.

For additional details concerning contraindications, warnings, precautions, adverse effects, and dosage and administration please see the enclosed full Prescribing Information.

Merck & Co., Inc. is a leading research-driven pharmaceutical products and services company. Merck discovers, develops, manufactures and markets a broad range of innovative products to improve human and animal health. The Merck Vaccine Division, a unit of Merck & Co., Inc. was created in 1991 to represent the Company's renewed commitment to the global vaccine business. A leader in vaccine research and development, the company introduced the first vaccines against measles, mumps, German measles, pneumoccocal pneumonia, chickenpox and hepatitis B. Through these complementary capabilities, Merck works to improve quality of life and contain overall health-care costs. Full prescribing information for Varivax(R) follows.

(A) trademark of MERCK & CO., Inc. Varivax is the Merck registered trademark for Varicella Virus Vaccine Live (Oka/Merck)

CONTACT: Donna Cary of Merck & Co., 215-652-5558