National childhood varicella vaccination program reduces chickenpox hospitalization rates

Since the varicella vaccine was introduced in the mid-1990s, the number of patients receiving medical care for chickenpox in the United States has decreased sharply—particularly among children, according to a study in the March issue of The Pediatric Infectious Disease Journal. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health, a leading provider of information and business intelligence for students, professionals, and institutions in medicine, nursing, allied health, and pharmacy.

"These results further emphasize the benefits of the national childhood varicella vaccination program in reducing rates of primary varicella infection," concludes the new study, led by Dr Samir S. Shah of the Children's Hospital of Philadelphia.

Chickenpox-related Office Visits Drop by Two-Thirds—Even More in Kids
Dr. Shah and colleagues used large national health care databases to compare rates of health care use for chickenpox and related problems in two periods: before (1993-95) and after (1996-2004) licensing of the chickenpox vaccine. By 2004, the national childhood varicella vaccination rate was nearly 90 percent. (The varicella vaccine protects against varicella zoster virus, which causes chickenpox.)

The results showed a significant two-thirds drop in the rate of ambulatory care (doctor's office or clinic) visits related to chickenpox: from 106 to 36 visits per 100,000 population. For infants and children aged 0 to 4 years, the rate of chickenpox-related office visits decreased by 98 percent.

The rate of hospitalizations related to chickenpox decreased by more than 50 percent: from about 31 to 15 per 100,000 population. This difference was significant in children less than 14 years of age. The reductions in younger patients are particularly important, because children and teens are at higher risk of rare but potentially serious complications of chickenpox.

Before and after the introduction of varicella vaccine, minority patients had higher rates of medical care for chickenpox-related problems, compared to white patients. However, the rate of chickenpox-related hospitalizations decreased for minority patients as well. The reasons for this racial difference are unclear, but could reflect differences in access to medical care, according to the study authors.

Previous studies showed that rates of death and hospitalization from chickenpox declined sharply after the introduction of varicella vaccine. Studies using insurance databases have shown reductions in ambulatory care visits for chickenpox—with corresponding reductions in costs. By using national health statistics, the new study provides important new information on trends in chickenpox-related medical care, including uninsured as well as insured patients.

"Varicella-related ambulatory visits and hospitalizations have decreased significantly in the period after licensure of the varicella vaccine," Dr. Shah and co-authors conclude. They call for continued studies to monitor the effectiveness of chickenpox vaccination. Information on ambulatory care visits is important because, though outbreaks of chickenpox do occur in vaccinated populations, they tend to be mild—and thus are more likely to be treated in the doctor's office than the hospital.