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Two doses of varicella vaccine highly effective for children
Shapiro E. J Infect Dis. 2011; doi:10.1093/infdis/jiq052.
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A two-dose varicella vaccine regimen has been confirmed highly effective in children and recommended in the United States, according to new findings from The Journal of Infectious Diseases.
In June 2006, after the CDC added a second dose of varicella vaccine to the routine immunization schedule for US children, researchers from Yale University were the first to assess the clinical effectiveness of two doses of the vaccine.
In a case-control study, Eugene D. Shapiro, MD, of the department of pediatrics at Yale University School of Medicine and Graduate School of Arts and Sciences, and colleagues conducted active surveillance to identify children aged 4 years and older who were thought to have varicella. The children were enrolled after June 30, 2006, in a pediatric practice in Connecticut.
Of the 71 case participants and 140 matched controls enrolled from July 2006 to January 2010:
- No cases (0%) vs. 22 controls (15.7%) received two doses of varicella vaccine.
- Sixty-six cases (93%) vs. 117 controls (83.6%) had received one dose of varicella vaccine.
- Five cases (7%) vs. one control (0.7%) did not receive varicella vaccine (P<.001).
Based on the results of the study, the two-dose regimen was highly effective at 98.3% (95% CI, 83.5-100) compared with 86% for one dose (95% CI, –44.5 to 99), the researchers reported.
“In the first 3.5 years since the recommendation for routine administration of a second dose of varicella vaccine, the odds of getting varicella are 95% lower among children aged 4 years and older who have received two doses of the vaccine compared with those who received one dose,” Shapiro told Infectious Disease News. “Parents and physicians should assure that all children (and adults) who received one dose of the varicella vaccine should receive a second dose.”
The two-dose varicella policy instituted in the United States will have future implications for national immunization programs in other countries that use the vaccine, the researchers wrote. – by Ashley DeNyse
These data from Shapiro and colleagues represent the first assessment of the effectiveness of the two-dose varicella vaccine. At 98.3%, these data validate the calculations of experts from the CDC’s Advisory Committee on Immunization Practices and the American Academy of Pediatrics Committee on Infectious Diseases made in 2006 when both groups approved a recommendation for routine use of two doses of varicella vaccine during childhood. It is anticipated that additional gains in varicella control will result from the two-dose vaccination program.
–David Kimberlin, MD
University of Alabama at Birmingham
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