By Sean Henahan, Access Excellence

WASHINGTON, D.C.- With the F.D.A. approval of a new varicella vaccine, chickenpox is no longer the only common childhood illnesses that cannot be prevented via inoculation.

The new vaccine is a lyophilized preparation of a common strain of live, attenuated varicella virus. Varicella virus is a member of the herpes virus and is the same virus that causes zoster, otherwise known as shingles, later in life. The FDA guidelines call for children from 12 months to 12 years of age who have not had chicken pox to receive a single subcutaneous injection of the vaccine. Adolescents and adults who have not had chickenpox will receive two doses given one to two months apart.

"The nation and the world should be pleased that another important achievement in disease prevention has been realized. After years of intense research and clinical trials, and at a time when 'wellness' and 'prevention' are becoming the standards of health care and medical economics, a vaccine against such a troublesome malady as chickenpox is welcome news. A point that may pass unnoticed is that this the first vaccine against a virus in the herpes family, which is in itself a significant step forward," sad Dr. Richard Duma, Director of the National Foundation for Infectious Diseases.

More than 95% of Americans get chickenpox, most before they reach the age of 15 years. The Centers for Disease Control estimates that four million cases of chicken pox occur each year. Having chicken pox confers long term natural immunity. Complications from chickenpox are quite rare. Nonetheless 9,000 people per year, most of whom are children, are hospitalized for complications of chickenpox each year. These complications can include concurrent infections with staphylococcus and streptococcus bacteria, pneumonia and neurologic problems including encephalitis. Each year 40 formerly healthy children die of complications of chickenpox.

"Parents have always assumed that chickenpox was an unpleasant fact of life. It was something they would hope wouldn't come at a terribly inconvenient time, such as vacations or holidays. Parents are often not aware that chickenpox can cause severe consequences, such as bacterial infections or pneumonia, even in healthy children. Fortunately, they can now help their children avoid getting the disease in the first place," said Dr. Anne Gershon, a professor of pediatrics at Columbia Presbyterian Medical Center in New York, who worked on the trials of the vaccine.

The vaccine was developed in Japan in the 1970's and has been approved for use in that country and several others for many years. However, the FDA often requires drug manufacturers to conduct more tests in this country as a condition of approval. This led to a ten year clinical testing phase during which nearly ten thousand children, along with 1600 adolescents and adults were treated and followed.

The clinical trials indicated that antibodies against varicella were present in more than 98% of patients after one year. The studies also confirmed the safety of the vaccine. The most common side effects were related to pain and swelling at the injection site. This is a common side effect with many vaccines. Fever, rash and itching were also seen, particularly among the adolescents and adults.

Follow-up studies lasting as long as six years have shown that a small percentage of patients, between one and three percent, develop chickenpox after being vaccinated. Further follow-up studies are underway in children who have received the vaccine.

An article in the Journal of the American Medical Association (2/2/94) suggests the vaccine may make economic sense. That study projected a savings of $384 million per year, $5.40 per dollar invested if chickenpox vaccination becomes routine. The study was based on a vaccine cost of $35 per dose and took into account the costs of medical care and the costs of work loss in association with chickenpox.

The vaccine may actually proffer greater benefit in the adolescent and adult populations. While chickenpox is rare in these age groups, it last longer and often takes a more severe course. Adults are nearly ten times more likely to require hospitalization for chickenpox than are children, and are more than 20 more likely to die from the disease.

Some important questions remain about the chicken pox vaccine. While the clinical studies have shown varicella antibodies persisting for one year after vaccination, the long term persistence of immunity is unknown. Moreover, the relationship between detectable immune responses and protection from chickenpox infection is not known. It is possible that booster shots may be required.

Transmitted: 95-03-22 22:15:30 EST

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