Studies have been released questioning the effectiveness of the varicella vaccine over time. Epidemiologists researched several chickenpox outbreaks since the advent of the vaccine. These outbreaks have occurred in schools with highly vaccinated populations.

Studies have found that the overall effectiveness of the vaccine is 87 percent (95% confidence interval, 81%-91%).  However, the vaccine is 97 percent effective in the first year after vaccination. In the 2 to 8 years after vaccination, the vaccine is only 84 percent effective. Most cases of chickenpox in children who have received the vaccine have been relatively mild.¹

The varicella vaccine was approved in 1995, when the youngest current Job Corps students were around 4 years old. Chances are some students on your center have been vaccinated and some have had chickenpox. Students who develop chickenpox while on center may have been vaccinated but are no longer immune to varicella. If a student or their parents are unsure about history of the disease or vaccine information, an enzyme immunoassay (EIA) test can be conducted to determine immunity. This test is often less expensive than the immunization.² If several students show signs of chickenpox, you may want to contact your local health department.

¹ Vazquez M, LaRussa PS, Gershon AA, Niccolai LM, Muehlenbein CE, Steinberg SP, Shapiro ED. Effectiveness over time of varicella vaccine. JAMA. 2004;291:851-855.

² Centers for Disease Control and Prevention, National Immunization Program. Varicella Vaccine. Available at: http://www.cdc.gov/nip/vaccine/varicella/faqs-clinic-vaccine.htm#7-serologic