First Vaccine for Chickenpox Passes Key Step

The first vaccine to prevent chickenpox took a major step toward federal approval Thursday when a key advisory committee concluded that the experimental vaccine is safe and effective against the common childhood disease that afflicts 4 million children annually.

Chickenpox, a highly contagious illness characterized by fever, weakness and a rash that itches and blisters, is virtually the only significant childhood ailment for which there has been no approved vaccine. Vaccines already are in widespread use for diphtheria, tetanus, pertussis (whooping cough), measles, mumps, rubella (German measles) and polio, among others.

In a nearly unanimous decision, the FDA vaccines advisory committee said: “There is available data to support claims of safety and efficacy for children, adolescents and adults.”

“We’re very pleased,” said Dr. Gordon Douglas, president of Merck & Co.’s vaccine division, which developed the vaccine. “We believe the vaccine is safe and effective, and will be a big advance in terms of children’s health in this country. We think that prevention is always far preferable to treatment.”

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While advisory committee decisions and recommendations are not binding on the agency, they typically wield considerable influence in FDA decision-making. If approval comes quickly, the vaccine could be available by summer.

Officials of Merck, which is based in Whitehouse Station, N.J., told the committee that its studies have shown the vaccine to be highly effective.

Dr. Jo White, senior director of the company’s research laboratories, told the committee that in a controlled study, the vaccine “provided 98% protection from . . . disease following one dose of vaccine in healthy children (whose progress was) followed for two years.”

In follow-up studies of more than 9,000 children over 12 years old, only 1% to 3% of them developed a mild form of the disease after they were exposed, she said.

Research conducted in a household setting--where exposure typically results in severe disease--demonstrated that the vaccine provided 98% protection, she said. She defined severe disease as cases in which an individual had “300 lesions or more and a temperature of 100 degrees Fahrenheit or higher.”

In its submissions to the FDA, the company has suggested that children 1 to 12 years old receive a single dose of the vaccine and that those 13 or older, including adults, be given two doses one to two months apart.

The vaccine has caused minimal side effects in a small percentage of children--with a mild rash the most serious.

A similar vaccine already is in use in Japan, Korea and several countries in Europe.

“I think this will be a very important addition to our vaccine arsenal,” said Dr. Richard Duma, executive director of the National Foundation for Infectious Diseases. “There are a lot of studies that indicate the vaccine will be cost-effective, that at least $4 or $5 will be saved for every dollar spent,” Duma added. “ If it is used widely, I think there’s a very good chance we can basically wave goodby to chickenpox.”

In normal, otherwise healthy children, chickenpox, or varicella, generally is a benign disease, although the rash can be quite severe. In some cases, complications can occur, resulting in hospitalizations and even deaths.

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“Children can get very sick from it--they are uncomfortable, they lose time from school, and parents have to stay home and take care of them,” Merck’s Douglas said. “Some get very sick and about 9,000 get hospitalized, and there are some deaths in normal children every year.”

Complications can include bacterial skin infections arising from the rash and, more rarely, encephalitis (infection of the brain), meningitis (infections of the covering of the brain) and Reye’s syndrome, a sometimes fatal illness that results when aspirin is given to children suffering from chickenpox or flu.

For most people, however--including children who get sick and the parents who must stay home and care for them--chickenpox is an uncomfortable, costly and inconvenient nuisance.

After the disease, individuals usually maintain a lifelong immunity to chickenpox and do not suffer further episodes. But the virus can reactivate later in life as shingles, a painful skin condition.