Successes of the Chickenpox Vaccine

Chickenpox vaccine has led to 90 percent decline in cases and hospitalizations

/ Author:  / Reviewed by: Robert Carlson, M.D Beth Bolt, RPh

(RxWiki News) Any time a new vaccine is introduced, researchers pay special attention to what happens in the next several decades to the disease that vaccine protects against. Chickenpox is no different.

A recent study found that cases of chickenpox have significantly dropped since the varicella, or chickenpox, vaccine was introduced in 1995.

Hospitalizations for chickenpox have also declined over this time.

The researchers determined that chickenpox cases were not occurring among older children or teens, a concern among some when the vaccine was introduced.

"Discuss vaccinations with your child's pediatrician."

The study, led by Roger Baxter, MD, of Kaiser Permanente Vaccine Study Center in Oakland, California, looked at the impact of introducing the chickenpox vaccine.

The researchers conducted five separate studies to examine how chickenpox has afflicted different groups before and after the introduction of the vaccine.

The first of these studies occurred from 1994 to 1995, just before the vaccine was introduced.

The remaining four studies occurred in 2000, 2003, 2006 and 2009, which allowed the researchers to see how the illness was showing up in the population over time after the vaccine had been introduced.

During each study, the researchers conducted phone interviews with approximately 8,000 members in the Kaiser Permanente of Northern California network.

All the participants involved were aged 5 to 19, and then rates of hospitalization for chickenpox were examined for all members of Kaiser Permanente of Northern California.

The researchers found that the total cases of chickenpox for those aged 5 to 19 decreased between 1995 and 2009 from 26 cases per 1,000 kids per year to 1 case per 1,000 kids per year.

This decrease represented approximately a 90 to 95 percent decline for each age group.

The researchers also found a drop in hospitalizations for chickenpox over that time period.

Between 1994 and 2009, the rate of hospitalizations for chickenpox dropped from 2.1 people per 100,000 to 0.25 people per 100,000, which is also a 90 percent drop.

These findings revealed that the number of cases of chickenpox and the hospitalizations form them have been dramatically reduced since the introduction of the vaccine.

The researchers found no evidence that introducing the vaccine led to greater illness among older children or teens.

The study was published June 9 in the journal Pediatrics. The research was funded by Merck Sharp & Dohme, Corp.

One author is an employee of Merck and holds Merck stocks. No other conflicts of interest from other authors were reported.

Review Date: 
June 8, 2014
Last Updated:
June 9, 2014