All children will be required to get a chickenpox vaccination before they are 19 months old, officials with the state Department of Health and Human Services announced Wednesday.

The chickenpox vaccine will be the 10th required by the state. It has been available since 1995 and is given to about 75 percent of children on a voluntary basis.

Other vaccines guard against measles, mumps, rubella, hepatitis B and polio, among others.

Children born on or after April 1, 2001, are subject to the new requirement, meaning parents must show proof of their children's immunization to enroll them in day care centers and public schools.

Even as the state presses forward with the new rules, a shortage of the vaccine has made it difficult for other states to enforce immunization schedules.

Merck and Co. is the only producer of chickenpox vaccine, and it has had difficulty meeting increasing demand.

Barbara Laymon, vaccine accountability manager with the state immunization branch, said Merck officials have assured the state that backlogs will be cleared by the end of April. Children in North Carolina are not expected to be hampered by manufacturing problems, she said.

North Carolina's efforts to add the chickenpox vaccine to its list of required inoculations had been proposed for years, but were delayed by funding issues.

The state pays for every child to get vaccines, although doctors may charge administration fees.

The universal vaccination program, which the state started in 1994, has eliminated financial barriers to immunizations. As a result, North Carolina led the nation in 2000 for immunization compliance, Laymon said, with 88 percent of the state's children receiving their shots.

Adding the chickenpox vaccine will cost $700,000 a year -- money that was found last fall despite the state's budget problems. Physicians say the money will be well-spent.

"The disease incidence has gone down dramatically," said Dr. Dennis Clements, professor of pediatrics at Duke University School of Medicine and a researcher who helped test the chickenpox vaccine in the 1980s.

"The vaccination rate in young kids is up to 80 percent, and there's been an 80 percent falloff in illness."

chickenpox is usually a mild disease characterized by fever and an itchy outbreak of blisters that cover the body.

But it can be serious, even deadly. Severe complications often arise when the rash becomes infected with a strep virus.

Before the vaccine came out in 1995, about 4 million people across the nation suffered from the illness each year, and it killed up to 100.

In June 1988, Rebecca Ellison Cole's 12-year-old son, Christopher Aaron Chinnes, died at Pitt Memorial Hospital in Greenville after he came down with chickenpox.

An asthmatic, Christopher was taking steroids when he developed the illness, and the steroids triggered a deadly response.

"He was in deep pain," said Cole, who now lives in Chapel Hill and has worked to promote the vaccine nationally. "Every organ in his body was destroyed. ... It was horrible. Absolutely horrible."

Cole testified before Congress and lobbied the General Assembly to make the chickenpox vaccine one of the required immunizations.

"I couldn't stand the thought of it happening to anybody else," Cole said. She said she is pleased the state's new rules have finally gone into effect.

Other parents, leery of the health consequences of childhood vaccines, have taken to the Internet to question the wisdom of requiring another one. Most of their concerns center on the measles, mumps and rubella vaccine, which has been suggested as a trigger for autism.

Clements said that the chickenpox vaccine appears to have few drawbacks.

Some people develop rashes after getting a shot, while others break out in a mild form of the disease, Clements said. The immunization is best offered in a single dose, he said, shortly after a baby's first birthday, because that is when the immune system is developed enough.