Rates of chicken pox drop dramatically when patients receive two doses of the varicella vaccine, according to a study in the journal JAMA Pediatrics. Researchers looked at two locations: Antelope Valley, Calif., and West Philadelphia to see what happened when the two-dose regimen was introduced in 2006. Antelope Valley saw a 76% decline in varicella between 2006 and 2010; West Philadelphia saw a 67% drop.
“Declines in varicella incidence were seen across all age groups…. Varicella-related hospitalizations in the active surveillance areas declined nearly 50% during the first five years of the two-dose varicella vaccination program. With full implementation of the two-dose varicella vaccination program, it may be possible to eliminate the most severe outcomes of varicella.”
West Philadelphia, a Philadelphia neighborhood, had about 272,000 residents as of 2010; Antelope Valley had about 373,000. The data for West Philadelphia were gathered by the Philadelphia Department of Public Health’s Kids Immunization Database. In Antelope Valley, Kaiser Permanente Southern California gathered the data through its Kaiser Immunization Tracking System.
Varicella incidence after 2-dose vaccine
The solid line represents Antelope Valley, Calif. The dotted line is for a neighborhood in Philadelphia.
Source: “Impact of a Routine Two-Dose Varicella Vaccination Program on Varicella Epidemiology,” JAMA Pediatrics, Oct. 7, 2013