Chickenpox Vaccine Works LESS Than Half The Time...
New study findings
indicate that, at least among one group of children, the varicella
vaccine is much less effective than previously reported.
New study findings indicate that, at least among one group of children, the varicella vaccine is much less effective than previously reported.
Dr. Jane Seward, from the us Centers for Disease Control and Prevention in Atlanta, and colleagues reported on their investigation of a recent outbreak of chickenpox at a New Hampshire day care center.
The outbreak in 23 children began with a child who had been vaccinated, contradicting the belief that such "breakthrough" cases are not contagious, Dr. Seward noted. The child, a 4-year-old, was confirmed not to have developed chickenpox infection from the vaccine, but probably developed it after exposure to a sibling with shingles.
Previous findings indicate that the vaccine's effectiveness ranges from 71% to 91%. In the current study, however, the effectiveness that was only about 40%.
41st Annual Interscience Conference on Antimicrobial Agents and Chemotherapy Chicago December 16, 2001
Scientists said on Thursday that vaccinating children against chickenpox (varicella) could increase the risk that adults would develop shingles, a painful blistering rash that is potentially dangerous in the elderly.
The team, at Britain's Public Health Laboratory Service (PHLS), said that although vaccination would save thousands of lives over time, thousands of elderly people could also die from the complications of shingles, known as herpes zoster.
Writing in the journal Vaccine, they called for a re-evaluation of the policy of mass chickenpox vaccination that has been introduced already in the United States and is imminent in many other countries. In 1995, the chickenpox vaccine was approved for use in children over 1 year of age in the US and is now required for school entry.
After a bout of naturally-occuring chickenpox, the varicella zoster virus remains dormant in the body and may reactivate decades later to cause shingles, a painful rash that typically strikes chickenpox veterans after the age of 60.
Marc Brisson and his team say their research shows that adults living with children have more exposure to the virus that causes chickenpox and enjoy high levels of protection against shingles. Being close to children means that adults are exposed to the virus, which acts like a booster vaccine against shingles, they believe. But if all children were vaccinated, adults who have had chickenpox would no longer be protected against developing shingles.
The researchers worked out a mathematical model that predicts that eliminating chickenpox in a country the size of the United States would prevent 186 million cases of the disease and 5,000 deaths over 50 years. However they said it could also result in 21 million more cases of shingles and 5,000 deaths.
The PHLS said in a statement it was working out what the impact might be
JAMA May 1, 2002;287(17):2211:
Maryland and federal health officials will converge on Takoma Park Elementary School next week to find out why at least 12 students contracted chickenpox in the past two months despite receiving vaccinations against the disease.
Of the 16 cases of chickenpox tallied so far at the Montgomery County school, all but four involved youngsters who reportedly received the vaccine before they were 3 years old.
Physicians are not required to report chickenpox to government agencies, and it isn't clear whether the number of cases logged at the school so far is accurate -- especially because some cases are so mild that parents aren't aware of them.
Officials with the Montgomery County Department of Health and Human Services, the state Department of Health and Mental Hygiene and the U.S. Centers for Disease Control and Prevention will use a survey to nail down the numbers and help whether the vaccine has failed in some way.
Jane Seward, acting chief of CDC's child vaccine and preventable diseases branch, said she is not alarmed by Takoma Park Elementary's outbreak.
It is possible the high percentage of cases among reportedly vaccinated children merely reflects the Maryland chickenpox vaccination rate, one of the highest in the nation, she said.
"That's what you start to see when a state achieves a high coverage rate for a vaccine," she said. In 1999, 78.5 percent of Maryland children in the target age group were vaccinated, the third-best performance of any state, she said.
Since chickenpox vaccine was licensed in 1995, its use has grown steadily, she said. Doctors never expected it to wipe out the illness; instead the vaccine is supposed to prevent chickenpox in 80 to 85 percent of those who receive it and prevent severe cases from developing in the rest, she said.
Severe cases bring hundreds of painful blisters, high fever, excruciating itchiness, possible infection caused by scratching, and decreased appetite caused by sores in the mouth.
In extreme cases, patients can develop pneumonia, brain infection or bleeding disorders, Seward said. CDC says more than 5,000 people are hospitalized and about 100 die of chickenpox nationwide each year.
Washington Post February 2, 2001; Page B08