January 3, 2011

Chickenpox Hospitalizations Dropped Since Vaccination Started

Government researchers reported on Monday that the number of Americans sent to hospitals each year due to a chickenpox infection has dropped by over two-thirds since routine vaccinations began in 1995.

Studies have shown that after vaccinations against chickenpox became standard, yearly rates of chickenpox infections in the U.S. dropped 80 percent to 90 percent over the next decades.

Researchers at the Centers for Disease Control and Prevention (CDC) looked at how rates of chickenpox-related hospitalizations have changed.

Some people develop potentially serious complications even though most cases include symptoms like an itchy rash, a fever, headache and fatigue.

Serious complications include skin infections, vomiting leading to dehydration, pneumonia and inflammation of the brain known as encephalitis.

The CDC researchers found that between 2000 and 2006, the number of hospitalizations for chickenpox complications stood at 0.1 for every 10,000 Americans.  That compared with a rate of 0.4 per 10,000 people each year between 1988 and 1995, which was before the vaccine was introduced.

Hospitalizations dropped by 71 percent during the study period.  Researchers estimate that the chickenpox vaccination has prevented a total of 50,000 hospitalizations between 2000 and 2006.

"This further supports what we've been seeing -- in that there have been great declines in severe (chickenpox) disease," said lead researcher Adriana S. Lopez.

Lopez told Reuters that many people see chickenpox as a mild illness.  However, she said that parents should be aware that complications can occur.

She said that although hospitalizations are down, children under the age of 4 still have the highest rates of illness severe enough to require hospital treatment.

"It's still important for parents to have their children vaccinated," Lopez told Reuters.

Children routinely received one dose of the vaccine between the ages of 12 months and 18 months during the study period.  In 2007, a second dose was added to the schedule, to be given between the ages of 4 and 6.

Adults and teenagers who had already gotten the vaccine were also advised to get the second dose.

The second dose was added because one dose of the vaccine prevents chickenpox in only 80 percent to 90 percent of recipients. 

According to Lopez's team, an important finding of the current study is that chickenpox hospitalizations declined by over two-thirds in each age group the researchers considered.

"It's great to see that in adults," Lopez said, noting that this is a sign of "herd immunity," which is when widespread vaccination in a population helps limit disease transmission.

According to the CDC, about 20 percent of people who see side effects from the vaccine have reported to having swelling or soreness at the injection site, and up to four percent develop a mild rash and some skin bumps that resemble chickenpox.

The agency said that serious side effects are rare.  According to the CDC, less than one in 1,000 recipients suffer fever-induced seizures, and problems like encephalitis and pneumonia have been reported for about two of every 100,000 doses of the vaccine.

"This is a very safe vaccine," Lopez told Reuters.


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