Chickenpox Vaccine Rules the Roost

Chickenpox vaccine effectiveness at ninety percent among US children

(RxWiki News) One of the most recent vaccines added to the childhood schedule is the chickenpox vaccine. Enough time has passed to learn more about how effective the vaccine is.

A recent study looked at the rates of chickenpox in vaccinated children over a 14-year period.

The researchers found that the vaccine was very effective – offering 90 percent protection to children who received the shot. It protected children against both varicella (chickenpox) and herpes zoster (shingles).

Even those children who did get chickenpox after being vaccinated had milder cases than were commonly seen in the US before the vaccine was available.

"Vaccinate your children according to the CDC schedule."

The study, led by Roger Baxter, MD, of the Kaiser Permanente Vaccine Study Center in Oakland, California, aimed to see how effective the chickenpox vaccine was over a 14-year period.

The chickenpox vaccine was first licensed for children aged 1 and older in the US in 1995. The CDC began recommending a booster dose in June 2006.

The researchers followed 7,585 children from 1995, when they got their first chickenpox vaccine shot at age 2, through 2009. About a third of them (2,826 children) received a booster dose between 2006 and 2009.

The researchers compared the rates of chickenpox and shingles among these children with the rates among US children before the chickenpox vaccine was available.

The researchers found that in one year, approximately 16 children out of 1,000 in this group got the chickenpox. This rate is about nine to ten times lower than the rate before the vaccine was introduced in the US.

Even the children who got chickenpox despite being vaccinated had mild cases. None of the children who received two doses of the vaccine developed chickenpox after the second shot during the study.

The researchers estimated that the chickenpox vaccine is 90 percent effective and does not appear to lose its effectiveness over time.

"This study confirmed that varicella vaccine is effective at preventing chicken pox, with no waning noted over a 14-year period," the researchers wrote. "One dose provided excellent protection against moderate to severe disease, and most cases occurred shortly after the cohort was vaccinated."

The researchers noted that rates of shingles were about 40 percent lower among children who were vaccinated as well, and that this data "also suggest that varicella vaccination may reduce the risks of herpes zoster (shingles) in vaccinated children."

The study was published April 1 in the journal Pediatrics. The research was funded by Merck Sharp and Dohme Corp. Three authors were Merck employees at the time of the study, and three have received research grants or consultancy fees from Novartis, GlaxoSmithKline, Sanofi Pasteur and the World Health Organization. Two authors declared no conflicts of interest.

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Review Date: 
March 28, 2013