Healio
Healio
April 21, 2010
2 min read
Save

Two-dose varicella vaccine shows promise in reducing infection

ATLANTA — The two-dose varicella vaccine were linked to significant decreases in incidence of disease in two Varicella Active Surveillance Project (VASP) sites: West Philadelphia and Antelope Valley, Calif., according to presenters at the 44th National Immunization Conference.

The Advisory Committee on Immunization Practices recommended the routine use of a two-dose varicella vaccine in June 2006 because of continued outbreaks occurring in schools, despite a decline in disease, hospitalization and death associated with the single-dose vaccine.

The implementation of a two-dose varicella vaccination program prompted researchers at the VASP’s West Philadelphia site to assess the effect that a second dose had on incidence of disease, according to Roderica Pierre, BA, of the Philadelphia Department of Public Health.

The researchers examined data on reported cases of varicella provided by VASP, and health care providers reported the amount of individual two-dose vaccines that they administered from 2003 to 2007, said Pierre. Information for 2008, however, was taken from Philadelphia’s Kids Immunization Database/Tracking System Registry.

Health care providers in West Philadelphia administered an average of more than 5,000 doses between 2003 and 2006, noted Pierre. This number was three to four times higher after introduction of the two-dose vaccine, according to the researchers, with more than 19,000 vaccines administered in 2007 and more than 15,000 in 2008.

Results also showed that the overall coverage for children aged 5 to 9 years increased to 30% in 2007 and 51% in 2008 during the two-dose vaccine era, according to Pierre. Data also indicated a 43% reduction in varicella incidence by 2008 in this population.

Researchers from VASP’s Antelope Valley site found similar results, according to Amanuel Hussein, BA, MSc, MSW, a research analyst for Los Angeles County.

The researchers compared the incidence of varicella and the proportion of breakthrough disease during the end of the single-dose varicella vaccination era with the introduction of the two-dose vaccine, Hussein said.

The researchers included verified cases of varicella infection with complete case reports for children residing in Antelope Valley. Breakthrough cases were defined as having illness for more than 42 days after immunization, and incidence rates were calculated using U.S. census data from 2005 to 2008.

Study data showed a 47.6% decline in varicella cases and disease incidence in most age groups after implementation of the two-dose vaccine, Pierre reported. Breakthrough cases also dropped 32.3% in all age groups.

A greater proportion of patients with varicella also presented with milder symptoms — including fewer lesions — after introduction of the two-dose vaccine, Hussein also noted. – by Melissa Foster

PERSPECTIVE

These data that examine varicella disease following the institution of two-dose varicella immunization are encouraging. Additional follow-up will be needed in other communities as well, but it is reassuring that varicella disease has declined with the new vaccination strategy.

– David Kimberlin, MD
Infectious Diseases in Children Editorial Board

For more information: