Expanding the scope of varicella vaccine debated

The 1995 introduction of universal varicella vaccination for children saved millions of dollars by reducing hospitalizations related to chicken pox, even among age groups not targeted to receive the shots, according to a study published in the September issue of Pediatrics.

"With a focus on extensive vaccination of children, we benefit all ages," said Matthew Davis, MD, lead author and assistant professor of pediatrics, internal medicine and public policy at the University of Michigan Health System.

The vaccine is recommended for all children older than 1 year, and the reductions in rate of hospitalizations were most significant among those younger than 4, decreasing from 4.19 per 10,000 people in 1994 to 0.53 per 10,000 in 2001. Reductions were also seen for adults and adolescents who should received the vaccine. For those older than 20, the rate declined from 0.29 per 10,000 in 1994 to 0.08 per 10,000 in 2001. For those ages 10-19, the rate went from 0.37 to 0.09.

Experts did acknowledge, though, that adult and adolescent vaccination is not a focus, leading them to believe that much of the vaccine's benefit among these age groups may have been reaped by people who probably never received it.

"In households that have children, there would be some adults who would be susceptible to chicken pox, and [adults are] more likely to end up in the hospital with more serious disease than children," said Dennis Murray, MD, chief of pediatric infectious disease at the Medical College of Georgia. "We're actually providing herd immunity."

Many experts view this paper as additional evidence that getting all children vaccinated against varicella is a good thing, and chicken pox is not as benign as most people think.

"Most folks feel that chicken pox isn't a very big deal, but in reality chicken pox has a substantial rate of serious complications," said Stanford Shulman, MD, chief of pediatric infectious disease at Children's Memorial Hospital in Chicago.

The authors agree but also argue that the paper offers an incentive to consider the shots more seriously for those outside the age range usually targeted by vaccination efforts.

"I'm hoping that this study may draw attention to the fact that varicella vaccine is available for adolescents and adults," Dr. Davis said. "As a primary care doctor myself, the severity of varicella illness among adults leads me to recommend it."

Getting adults and teenagers their shots, however, is a trickier proposition. The child immunization infrastructure is well-established, and adding another shot in the arm usually causes minimal disruption. The infrastructure after this age range is not quite as sophisticated, and vaccination levels tend to be much lower.

Also, although kids only need one shot, those older than 12 need them two, four to eight weeks apart. With only 5% to 10% of adults and adolescents actually eligible for the vaccine, most physicians would also want to test for the presence of varicella antibodies before administering it. This all adds to the cost and hassle.

"The bottom line is to keep trying to hone in on eliminating it in the pediatric population," said Laurene Mascola, MD, chief of the acute communicable disease control program at Los Angeles County Dept. of Health Services. "But it's always a good thing for internists to ask if a patient had varicella as a child. ... Most adult practitioners aren't routinely vaccinating people unless they're elderly. Even then, we don't do a great job."

Also for adults, particularly the elderly, most physicians are more concerned about shingles. This study did not include data about shingles-related hospitalizations. But there is work to address the issue. The Shingles Prevention Study is examining the use of high doses of the varicella vaccine in elderly people to determine if it will prevent shingles. Those results are expected at the end of this year.