Study: Chickenpox vaccine reduces adults’ odds of illness, complications

From staff reports

ATLANTA (CNN) -- A vaccine that prevents most cases of chickenpox is effective in protecting adults from brain inflammation, pneumonia and other serious complications that may occur with chickenpox, researchers announced Thursday.

Immunization is recommended for adults who have not had chickenpox, the researchers said in a report for members of the Infectious Diseases Society of America, meeting this week in New Orleans.

Chickenpox, usually a childhood disease, also strikes adults. They are more likely than children to experience complications and death, according to the U.S. Centers for Disease Control and Prevention (CDC).

About 85 percent of adults who have not had chickenpox and haven’t been vaccinated will get the sickness when exposed to the disease, said Dr. Krow Ampofo, who led the research. The infection rate drops to about 20 percent among vaccinated adults who are later exposed to the chickenpox virus.

"They have fewer complications," Ampofo said. "It’s a milder form. Recovery time is quicker."

One of the most serious complications of chickenpox, especially for adults, is encephalitis. It is an inflammation of the brain that can cause loss of consciousness, seizures, muscle weakness, sudden severe dementia, memory loss, withdrawal from social interaction and impaired judgment, according to the CDC.

Milder symptoms include confusion, sudden fever, headache, vomiting, photophobia (abnormal visual sensitivity to light), stiff neck, stiff back, drowsiness, clumsiness, unsteady walk and irritability.

Ampofo, a pediatric infectious-disease specialist at Columbia Presbyterian Hospital, New York City, said rates of infections did not decrease significantly during the first three years the chickenpox vaccine was available for U.S. children, beginning in 1995.

Since 1998, as more and more children were vaccinated, the incidence of chickenpox has declined, he said. As additional transmission routes are broken by the expanding use of the vaccine, the chickenpox virus finds fewer hospitable hosts.

"It may become eradicated," said Ampofo.

The vaccine is for healthy children 12 months of age or older and for adolescents and adults who have not had chickenpox. A simple test can determine whether a person has had the illness, Ampofo said. Usually, having the disease prevents a person from a second infection. For adults who may be susceptible to chickenpox, he recommended visiting a physician.

"Despite the fact that adults account for only 5 percent of varicella (chickenpox) cases per year," a CDC report said, "they account for a disproportionate number of deaths (55 percent) and hospitalizations (33 percent) compared with children."

Ampofo and his colleagues studied the cases of 557 vaccinated adults. "Among those who did contract chickenpox, the disease was generally mild with an average of 54 skin lesions or blisters," he said.

A severe case may produce more than 500 lesions, and the average is about 350, according to the CDC. Chickenpox is contagious one to two days before the rash appears and until all blisters have formed scabs. Chickenpox develops within 10 to 21 days after contact with an infected person.

An itchy rash develops into skin blisters that dry and become scabs in four to five days, CDC officials said. The rash, often the first sign of chickenpox, is sometimes accompanied by fever and malaise, which is usually more severe in adults.

Ampofo said one complication of chickenpox is a secondary skin infection caused by bacteria. Vesicles on the face and body can result in deep scars.

Before vaccinating began nationwide in 1995, there were approximately 11,000 hospitalizations and 100 deaths from chickenpox annually in the United States, CDC officials said. The cost of caring for U.S. children of normal health who contract chickenpox was estimated at $918 million in 1993, two years before introduction of the vaccine.

By 1999, CDC officials detected a dramatic decline in cases and the typical springtime increase in chickenpox cases did not occur.

Since chickenpox is highly contagious, more than 95 percent of Americans have gotten the disease by adulthood in pre-vaccination years.

The virus spreads from person to person by direct contact or through the air, according to a CDC report. Approximately 90 percent of persons in a household who have not had chickenpox will get it if exposed to an infected family member.

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U.S. Centers for Disease Control and Prevention
National Institutes of Health

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