Childhood Diseases

15 March 2007

2nd chickenpox shot advised

Protection against chickenpox slowly fades in children immunised against the disease, suggests a study that adds support to a recommendation for a booster shot of the vaccine.

Protection against chickenpox slowly fades in children immunised against the disease, suggests a study that adds support to a recommendation for a booster shot of the vaccine.

The study found the incidence of chicken pox increased over time among vaccinated children - from 1.6 cases per person-year one year after immunisation to 9 cases per person-year five years later and more than 58 cases per person-year nine years later, according to the report.

"This is the kind of monitoring we do to check a vaccination program," said senior researcher Dr Jane F. Seward, acting deputy director of the US Centres for Disease Control and Prevention's division of viral diseases. "This is the first time monitoring shows an increase in the number of cases over time."

Seward's team published the findings in the March 15 issue of the New England Journal of Medicine.

A vaccine against varicella, the medical name for chickenpox, was introduced in 1995 with a recommendation that it be given during the first year of life. Last year, a recommendation for a second shot at 4 to 6 years of age was added by the American Academy of Paediatrics and other medical bodies.

No vaccine is perfect
"No vaccine we have is 100 percent perfect," explained Dr Robert Frenck, a professor of paediatrics in infectious diseases at Cincinnati Children's Hospital and a member of the American Academy of Paediatrics committee for infectious diseases. "You have people who don't respond or lose immunity over time."

Chickenpox is rarely fatal, but it can cause an outbreak of hundreds of temporarily disfiguring open sores. The cases found in the study - which focused on immunised children in Antelope Valley, California, northeast of Los Angeles - tended to be relatively mild, Seward said.

"In general, the cases were very modified from natural varicella," she said. "So, the vaccine does appear to stand up."

However, the study also suggests that "there is a greater chance of the disease not being mild over time," Seward said. "We need to keep following this group to see if it translates into more disease over time."

About 90% effective
"The important thing is that the [first-shot] protection is about 90 percent effective," Frenck said. "There was an 85 percent reduction in cases of varicella over 10 years."

A new multiple vaccine, approved last year, should make it easier for children to get both the first and recommended second shot, Frenck said. Protection against chicken pox has been added to the MMR vaccine, aimed at measles, mumps and rubella (German measles).

A second shot offers advantages in addition to protection against a childhood outbreak, Seward said, since chickenpox can occur in adults. "There is definitely improved immune response after the second dose. There is better immunity in the long term," she said. – (HealthDayNews)

Read more:
Second chickenpox shot for your kids
Chickenpox vaccine still works

March 2007


Read Health24’s Comments Policy

Comment on this story
Comments have been closed for this article.

Ask the Expert


Prof Eugene Weinberg worked in the Paediatrics Department of the Red Cross Children’s Hospital for many years. He is presently a paediatric allergist at the Allergy Diagnostic Unit of the UCT Lung Institute in Mowbray.

Still have a question?

Get free advice from our panel of experts

The information provided does not constitute a diagnosis of your condition. You should consult a medical practitioner or other appropriate health care professional for a physical exmanication, diagnosis and formal advice. Health24 and the expert accept no responsibility or liability for any damage or personal harm you may suffer resulting from making use of this content.

* You must accept our condition

Forum Rules